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1
Chowdhury, Maisha, and Cordula Enenkel. "Intracellular Dynamics of the Ubiquitin-Proteasome-System." F1000Research 4 (July 24, 2015): 367. http://dx.doi.org/10.12688/f1000research.6835.1.
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The ubiquitin-proteasome system is the major degradation pathway for short-lived proteins in eukaryotic cells. Targets of the ubiquitin-proteasome-system are proteins regulating a broad range of cellular processes including cell cycle progression, gene expression, the quality control of proteostasis and the response to geno- and proteotoxic stress. Prior to degradation, the proteasomal substrate is marked with a poly-ubiquitin chain. The key protease of the ubiquitin system is the proteasome. In dividing cells, proteasomes exist as holo-enzymes composed of regulatory and core particles. The regulatory complex confers ubiquitin-recognition and ATP dependence on proteasomal protein degradation. The catalytic sites are located in the proteasome core particle. Proteasome holo-enzymes are predominantly nuclear suggesting a major requirement for proteasomal proteolysis in the nucleus. In cell cycle arrested mammalian or quiescent yeast cells, proteasomes deplete from the nucleus and accumulate in granules at the nuclear envelope (NE) / endoplasmic reticulum (ER) membranes. In prolonged quiescence, proteasome granules drop off the NE / ER membranes and migrate as stable organelles throughout the cytoplasm, as thoroughly investigated in yeast. When quiescence yeast cells are allowed to resume growth, proteasome granules clear and proteasomes are rapidly imported into the nucleus.Here, we summarize our knowledge about the enigmatic structure of proteasome storage granules and the trafficking of proteasomes and their substrates between the cyto- and nucleoplasm.Most of our current knowledge is based on studies in yeast. Their translation to mammalian cells promises to provide keen insight into protein degradation in non-dividing cells which comprise the majority of our body’s cells.
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Chowdhury, Maisha, and Cordula Enenkel. "Intracellular Dynamics of the Ubiquitin-Proteasome-System." F1000Research 4 (September 28, 2015): 367. http://dx.doi.org/10.12688/f1000research.6835.2.
Full textAbstract:
The ubiquitin-proteasome system is the major degradation pathway for short-lived proteins in eukaryotic cells. Targets of the ubiquitin-proteasome-system are proteins regulating a broad range of cellular processes including cell cycle progression, gene expression, the quality control of proteostasis and the response to geno- and proteotoxic stress. Prior to degradation, the proteasomal substrate is marked with a poly-ubiquitin chain. The key protease of the ubiquitin system is the proteasome. In dividing cells, proteasomes exist as holo-enzymes composed of regulatory and core particles. The regulatory complex confers ubiquitin-recognition and ATP dependence on proteasomal protein degradation. The catalytic sites are located in the proteasome core particle. Proteasome holo-enzymes are predominantly nuclear suggesting a major requirement for proteasomal proteolysis in the nucleus. In cell cycle arrested mammalian or quiescent yeast cells, proteasomes deplete from the nucleus and accumulate in granules at the nuclear envelope (NE) / endoplasmic reticulum ( ER) membranes. In prolonged quiescence, proteasome granules drop off the nuclear envelopeNE / ER membranes and migrate as droplet-like entitiesstable organelles throughout the cytoplasm, as thoroughly investigated in yeast. When quiescence yeast cells are allowed to resume growth, proteasome granules clear and proteasomes are rapidly imported into the nucleus.Here, we summarize our knowledge about the enigmatic structure of proteasome storage granules and the trafficking of proteasomes and their substrates between the cyto- and nucleoplasm.Most of our current knowledge is based on studies in yeast. Their translation to mammalian cells promises to provide keen insight into protein degradation in non-dividing cells, which comprise the majority of our body’s cells.
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Pedrycz, Agnieszka, and Agnieszka Kramkowska. "Mechanisms promoting and inhibiting the process of proteasomal degradation of cells." Current Problems of Psychiatry 17, no. 1 (March 1, 2016): 47–57. http://dx.doi.org/10.1515/cpp-2016-0007.
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AbstractDefects in the process of degradation of unneeded cellular proteins underlie many diseases. This article discusses one of the most important systems of removal of abnormal proteins. It describes the process of ubiquitination of proteins for proteasome degradation. It also describes the structure of the 26S and 20S proteasomes and the mechanism of ubiquitin-proteasome system. Proteasome proteolytic system is highly specialized and organized. Protease-proteasome 26S is particularly important for proper cell functioning. It recognizes and degrades marked proteins. Inhibition of proteasome pathway leads to cell cycle arrest and apoptosis.Efficient degradation of cellular proteins by UPS (the ubiquitin - proteasome system) - is important for signal transduction, transcriptional regulation, response to stress and the activity control of cell receptors.The development of many diseases has its origin in the dysfunction of the UPS route. This group includes diseases such as cancer, neurodegenerative disorders, immune-mediated diseases and infectious diseases. Development of effective methods for pharmacological intervention in the functioning of this system has become a great challenge. The use of specific, low molecular-weight proteasome inhibitors and enzymes catalyzing the ubiquitination gives hope for new, targeted therapies.
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Imkamp, Frank, Michal Ziemski, and Eilika Weber-Ban. "Pupylation-dependent and -independent proteasomal degradation in mycobacteria." Biomolecular Concepts 6, no. 4 (August 1, 2015): 285–301. http://dx.doi.org/10.1515/bmc-2015-0017.
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AbstractBacteria make use of compartmentalizing protease complexes, similar in architecture but not homologous to the eukaryotic proteasome, for the selective and processive removal of proteins. Mycobacteria as members of the actinobacteria harbor proteasomes in addition to the canonical bacterial degradation complexes. Mycobacterial proteasomal degradation, although not essential during normal growth, becomes critical for survival under particular environmental conditions, like, for example, during persistence of the pathogenic Mycobacterium tuberculosis in host macrophages or of environmental mycobacteria under starvation. Recruitment of protein substrates for proteasomal degradation is usually mediated by pupylation, the post-translational modification of lysine side chains with the prokaryotic ubiquitin-like protein Pup. This substrate recruitment strategy is functionally reminiscent of ubiquitination in eukaryotes, but is the result of convergent evolution, relying on chemically and structurally distinct enzymes. Pupylated substrates are recognized by the ATP-dependent proteasomal regulator Mpa that associates with the 20S proteasome core. A pupylation-independent proteasome degradation pathway has recently been discovered that is mediated by the ATP-independent bacterial proteasome activator Bpa (also referred to as PafE), and that appears to play a role under stress conditions. In this review, mechanistic principles of bacterial proteasomal degradation are discussed and compared with functionally related elements of the eukaryotic ubiquitin-proteasome system. Special attention is given to an understanding on the molecular level based on structural and biochemical analysis. Wherever available, discussion of in vivo studies is included to highlight the biological significance of this unusual bacterial degradation pathway.
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Schipper-Krom, Sabine, Katrin Juenemann, and Eric A. J. Reits. "The Ubiquitin-Proteasome System in Huntington’s Disease: Are Proteasomes Impaired, Initiators of Disease, or Coming to the Rescue?" Biochemistry Research International 2012 (2012): 1–12. http://dx.doi.org/10.1155/2012/837015.
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Huntington’s disease is a progressive neurodegenerative disease, caused by a polyglutamine expansion in the huntingtin protein. A prominent hallmark of the disease is the presence of intracellular aggregates initiated by N-terminal huntingtin fragments containing the polyglutamine repeat, which recruit components of the ubiquitin-proteasome system. While it is commonly thought that proteasomes are irreversibly sequestered into these aggregates leading to impairment of the ubiquitin-proteasome system, the data on proteasomal impairment in Huntington’s disease is contradictory. In addition, it has been suggested that proteasomes are unable to actually cleave polyglutamine sequencesin vitro, thereby releasing aggregation-prone polyglutamine peptides in cells. Here, we discuss how the proteasome is involved in the various stages of polyglutamine aggregation in Huntington’s disease, and how alterations in activity may improve clearance of mutant huntingtin fragments.
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Ding, Youming, Xiaoyan Chen, Bin Wang, Bin Yu, Jianhui Ge, and Xiaokang Shi. "Quercetin suppresses the chymotrypsin-like activity of proteasome via inhibition of MEK1/ERK1/2 signaling pathway in hepatocellular carcinoma HepG2 cells." Canadian Journal of Physiology and Pharmacology 96, no. 5 (May 2018): 521–26. http://dx.doi.org/10.1139/cjpp-2017-0655.
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The proteasomal system is a promising target for cancer treatment. Quercetin (Que), a flavonoid compound with antitumor ability, displays the inhibitory effect on proteasome activity. However, the underlying molecular mechanisms are ill defined. The present study found that Que treatment significantly reduced the chymotrypsin-like protease activity of proteasome whereas the trypsin- and caspase-like protease activities remained unchanged in HepG2 cancer cells, along with activation of p38 MAPK and JNK and reduction of ERK1/2 phosphorylation. Que-reduced proteasome activity could not be reverted by inhibition of p38 MAPK and JNK signaling pathway. In addition, MEK1 overexpression or knockdown upregulated or downregulated the chymotrypsin-like protease activity of proteasome, respectively. Both Que and MEK1/ERK1/2 inhibitor attenuated the expression levels of proteasome β subunits. These results indicate that Que-induced suppression of MEK1/ERK1/2 signaling and subsequent reduction of proteasome β subunits is responsible for its inhibitory impacts on proteasome activity.
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Goebel, Tatjana, Simone Mausbach, Andreas Tuermer, Heba Eltahir, Dominic Winter, Volkmar Gieselmann, and Melanie Thelen. "Proteaphagy in Mammalian Cells Can Function Independent of ATG5/ATG7." Molecular & Cellular Proteomics 19, no. 7 (April 16, 2020): 1120–31. http://dx.doi.org/10.1074/mcp.ra120.001983.
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The degradation of intra- and extracellular proteins is essential in all cell types and mediated by two systems, the ubiquitin-proteasome system (UPS) and the autophagy-lysosome pathway. This study investigates the changes in autophagosomal and lysosomal proteomes upon inhibition of proteasomes by bortezomib (BTZ) or MG132. We find an increased abundance of more than 50 proteins in lysosomes of cells in which the proteasome is inhibited. Among those are dihydrofolate reductase (DHFR), β-Catenin and 3-hydroxy-3-methylglutaryl-coenzym-A (HMGCoA)-reductase. Because these proteins are known to be degraded by the proteasome they seem to be compensatorily delivered to the autophagosomal pathway when the proteasome is inactivated. Surprisingly, most of the proteins which show increased amounts in the lysosomes of BTZ or MG132 treated cells are proteasomal subunits. Thus an inactivated, non-functional proteasome is delivered to the autophagic pathway. Native gel electrophoresis shows that the proteasome reaches the lysosome intact and not disassembled. Adaptor proteins, which target proteasomes to autophagy, have been described in Arabidopsis, Saccharomyces and upon starvation in mammalians. However, in cell lines deficient of these proteins or their mammalian orthologues, respectively, the transfer of proteasomes to the lysosome is not impaired. Obviously, these proteins do not play a role as autophagy adaptor proteins in mammalian cells. We can also show that chaperone-mediated autophagy (CMA) does not participate in the proteasome delivery to the lysosomes. In autophagy-related (ATG)-5 and ATG7 deficient cells the delivery of inactivated proteasomes to the autophagic pathway was only partially blocked, indicating the existence of at least two different pathways by which inactivated proteasomes can be delivered to the lysosome in mammalian cells.
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Gu, Xinjie, and Shutao Ma. "Recent Advances in the Discovery of Novel Peptide Inhibitors Targeting 26S Proteasome." Anti-Cancer Agents in Medicinal Chemistry 18, no. 12 (January 29, 2019): 1656–73. http://dx.doi.org/10.2174/1871520618666180813120012.
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Background: The 26S proteasome is a proteolytic complex of multimeric protease, which operates at the executive end of the Ubiquitin-Proteasome System (UPS) and degrades the polyubiquitylated proteins. Methods: After a brief introduction of 26S proteasome and Ubiquitin-Proteasome System (UPS), this review focuses on the structure and function of the 26S proteasome in intracellular protein level regulation. Then, physiological regulation mechanisms and processes are elaborated. In addition, the advantages and defects of approved 26S proteasome inhibitors were discussed. Finally, we summarized the novel peptide 26S proteasome inhibitors according to their structural classifications, highlighting their design strategies, inhibitory activity and Structure-Activity Relationships (SARs). Results: Cellular function maintenance relies on the proteasome metabolizing intracellular proteins to control intracellular protein levels, which is especially important for cancer cells to survive and proliferate. In primary tumors, proteasomes had a higher level and more potent activity. Currently, the approved small peptide inhibitors have proved their specific 26S proteasome inhibitory effects and considerable antitumor activities, but with obvious defects. Increasingly, novel peptide inhibitors are emerging and possess promising values in cancer therapy. Conclusion: Overall, the 26S proteasome is an efficient therapeutic target and novel 26S proteasome inhibitors hold potency for cancer therapy.
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Bard, Jared A. M., Ellen A. Goodall, Eric R. Greene, Erik Jonsson, Ken C. Dong, and Andreas Martin. "Structure and Function of the 26S Proteasome." Annual Review of Biochemistry 87, no. 1 (June 20, 2018): 697–724. http://dx.doi.org/10.1146/annurev-biochem-062917-011931.
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As the endpoint for the ubiquitin-proteasome system, the 26S proteasome is the principal proteolytic machine responsible for regulated protein degradation in eukaryotic cells. The proteasome's cellular functions range from general protein homeostasis and stress response to the control of vital processes such as cell division and signal transduction. To reliably process all the proteins presented to it in the complex cellular environment, the proteasome must combine high promiscuity with exceptional substrate selectivity. Recent structural and biochemical studies have shed new light on the many steps involved in proteasomal substrate processing, including recognition, deubiquitination, and ATP-driven translocation and unfolding. In addition, these studies revealed a complex conformational landscape that ensures proper substrate selection before the proteasome commits to processive degradation. These advances in our understanding of the proteasome's intricate machinery set the stage for future studies on how the proteasome functions as a major regulator of the eukaryotic proteome.
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Yadav, Dhananjay, Ji Yeon Lee, Nidhi Puranik, Pallavi S. Chauhan, Vishal Chavda, Jun-O. Jin, and Peter C. W. Lee. "Modulating the Ubiquitin–Proteasome System: A Therapeutic Strategy for Autoimmune Diseases." Cells 11, no. 7 (March 24, 2022): 1093. http://dx.doi.org/10.3390/cells11071093.
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Multiple sclerosis (MS) is an autoimmune, neurodegenerative disease associated with the central nervous system (CNS). Autoimmunity is caused by an abnormal immune response to self-antigens, which results in chronic inflammation and tissue death. Ubiquitination is a post-translational modification in which ubiquitin molecules are attached to proteins by ubiquitinating enzymes, and then the modified proteins are degraded by the proteasome system. In addition to regulating proteasomal degradation of proteins, ubiquitination also regulates other cellular functions that are independent of proteasomal degradation. It plays a vital role in intracellular protein turnover and immune signaling and responses. The ubiquitin–proteasome system (UPS) is primarily responsible for the nonlysosomal proteolysis of intracellular proteins. The 26S proteasome is a multicatalytic adenosine-triphosphate-dependent protease that recognizes ubiquitin covalently attached to particular proteins and targets them for degradation. Damaged, oxidized, or misfolded proteins, as well as regulatory proteins that govern many essential cellular functions, are removed by this degradation pathway. When this system is affected, cellular homeostasis is altered, resulting in the induction of a range of diseases. This review discusses the biochemistry and molecular biology of the UPS, including its role in the development of MS and proteinopathies. Potential therapies and targets involving the UPS are also addressed.
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Bellavista, Elena, Aurelia Santoro, Daniela Galimberti, Cristoforo Comi, Fabio Luciani, and Michele Mishto. "Current Understanding on the Role of Standard and Immunoproteasomes in Inflammatory/Immunological Pathways of Multiple Sclerosis." Autoimmune Diseases 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/739705.
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The ubiquitin-proteasome system is the major intracellular molecular machinery for protein degradation and maintenance of protein homeostasis in most human cells. As ubiquitin-proteasome system plays a critical role in the regulation of the immune system, it might also influence the development and progression of multiple sclerosis (MS). Bothex vivoanalyses and animal models suggest that activity and composition of ubiquitin-proteasome system are altered in MS. Proteasome isoforms endowed of immunosubunits may affect the functionality of different cell types such as CD8+and CD4+T cells and B cells as well as neurons during MS development. Furthermore, the study of proteasome-related biomarkers, such as proteasome antibodies and circulating proteasomes, may represent a field of interest in MS. Proteasome inhibitors are already used as treatment for cancer and the recent development of inhibitors selective for immunoproteasome subunits may soon represent novel therapeutic approaches to the different forms of MS. In this review we describe the current knowledge on the potential role of proteasomes in MS and discuss thepro et contraof possible therapies for MS targeting proteasome isoforms.
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Sutovsky, Peter. "Sperm proteasome and fertilization." REPRODUCTION 142, no. 1 (July 2011): 1–14. http://dx.doi.org/10.1530/rep-11-0041.
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The omnipresent ubiquitin–proteasome system (UPS) is an ATP-dependent enzymatic machinery that targets substrate proteins for degradation by the 26S proteasome by tagging them with an isopeptide chain composed of covalently linked molecules of ubiquitin, a small chaperone protein. The current knowledge of UPS involvement in the process of sperm penetration through vitelline coat (VC) during human and animal fertilization is reviewed in this study, with attention also being given to sperm capacitation and acrosome reaction/exocytosis. In ascidians, spermatozoa release ubiquitin-activating and conjugating enzymes, proteasomes, and unconjugated ubiquitin to first ubiquitinate and then degrade the sperm receptor on the VC; in echinoderms and mammals, the VC (zona pellucida/ZP in mammals) is ubiquitinated during oogenesis and the sperm receptor degraded during fertilization. Various proteasomal subunits and associated enzymes have been detected in spermatozoa and localized to sperm acrosome and other sperm structures. By using specific fluorometric substrates, proteasome-specific proteolytic and deubiquitinating activities can be measured in live, intact spermatozoa and in sperm protein extracts. The requirement of proteasomal proteolysis during fertilization has been documented by the application of various proteasome-specific inhibitors and antibodies. A similar effect was achieved by depletion of sperm-surface ATP. Degradation of VC/ZP-associated sperm receptor proteins by sperm-borne proteasomes has been demonstrated in ascidians and sea urchins. On the applied side, polyspermy has been ameliorated by modulating sperm-associated deubiquitinating enzymes. Diagnostic and therapeutic applications could emerge in human reproductive medicine. Altogether, the studies on sperm proteasome indicate that animal fertilization is controlled in part by a unique, gamete associated, extracellular UPS.
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Liu, Jinbao, Hanqiao Zheng, Mingxin Tang, Youn-Chul Ryu, and Xuejun Wang. "A therapeutic dose of doxorubicin activates ubiquitin-proteasome system-mediated proteolysis by acting on both the ubiquitination apparatus and proteasome." American Journal of Physiology-Heart and Circulatory Physiology 295, no. 6 (December 2008): H2541—H2550. http://dx.doi.org/10.1152/ajpheart.01052.2008.
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The ubiquitin proteasome system (UPS) degrades abnormal proteins and most unneeded normal proteins, thereby playing a critical role in protein homeostasis in the cell. Proteasome inhibition is effective in treating certain forms of cancer, while UPS dysfunction is increasingly implicated in the pathogenesis of many severe and yet common diseases. It has been previously shown that doxorubicin (Dox) enhances the degradation of a UPS surrogate substrate in mouse hearts. To address the underlying mechanism, in the present study, we report that 1) Dox not only enhances the degradation of an exogenous UPS reporter (GFPu) but also antagonizes the proteasome inhibitor-induced accumulation of endogenous substrates (e.g., β-catenin and c-Jun) of the UPS in cultured NIH 3T3 cells and cardiomyocytes; 2) Dox facilitates the in vitro degradation of GFPu and c-Jun by the reconstituted UPS via the enhancement of proteasomal function; 3) Dox at a therapeutically relevant dose directly stimulates the peptidase activities of purified 20S proteasomes; and 4) Dox increases, whereas proteasome inhibition decreases, E3 ligase COOH-terminus of heat shock protein cognate 70 in 3T3 cells via a posttranscriptional mechanism. These new findings suggest that Dox activates the UPS by acting directly on both the ubiquitination apparatus and proteasome.
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Dahlmann, Burkhardt. "Proteasomes." Essays in Biochemistry 41 (October 1, 2005): 31–48. http://dx.doi.org/10.1042/bse0410031.
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The major enzyme system catalysing the degradation of intracellular proteins is the proteasome system. A central inner chamber of the cylinder-shaped 20 S proteasome contains the active site, formed by N-terminal threonine residues. The 20 S proteasomes are extremely inefficient in degrading folded protein substrates and therefore one or two multisubunit 19 S regulatory particles bind to one or both ends of the 20 S proteasome cylinder, forming 26 S and 30 S proteasomes respectively. These regulatory complexes are able to bind proteins marked as proteasome substrates by prior conjugation with polyubiquitin chains, and initiate their unfolding and translocation into the proteolytic chamber of the 20 S proteasome, where they are broken down into peptides of 3–25 amino acids. The polyubiquitin tag is removed from the substrate protein by the deubiquitinating activity of the 19 S regulator complex. Under conditions of an intensified immune response, many eukaryotic cells adapt by replacing standard 20 S proteasomes with immuno-proteasomes and/or generating the proteasome activator complex, PA28. Both of these adaptations change the protein-breakdown process for optimized generation of antigenic peptide epitopes that are presented by the class I MHCs. Hybrid proteasomes (19 S regulator–20 S proteasome–PA28) may have a special function during the immune response. The functions of other proteasome accessory complexes, such as PA200 and PI31 are still under investigation.
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Kondakova, Irina V., Elena E. Shashova, Evgenia A. Sidenko, Tatiana M. Astakhova, Liudmila A. Zakharova, and Natalia P. Sharova. "Estrogen Receptors and Ubiquitin Proteasome System: Mutual Regulation." Biomolecules 10, no. 4 (March 26, 2020): 500. http://dx.doi.org/10.3390/biom10040500.
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This review provides information on the structure of estrogen receptors (ERs), their localization and functions in mammalian cells. Additionally, the structure of proteasomes and mechanisms of protein ubiquitination and cleavage are described. According to the modern concept, the ubiquitin proteasome system (UPS) is involved in the regulation of the activity of ERs in several ways. First, UPS performs the ubiquitination of ERs with a change in their functional activity. Second, UPS degrades ERs and their transcriptional regulators. Third, UPS affects the expression of ER genes. In addition, the opportunity of the regulation of proteasome functioning by ERs—in particular, the expression of immune proteasomes—is discussed. Understanding the complex mechanisms underlying the regulation of ERs and proteasomes has great prospects for the development of new therapeutic agents that can make a significant contribution to the treatment of diseases associated with the impaired function of these biomolecules.
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Tomita, Takuya. "Structural and biochemical elements of efficiently degradable proteasome substrates." Journal of Biochemistry 171, no. 3 (December 30, 2021): 261–68. http://dx.doi.org/10.1093/jb/mvab157.
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Abstract Most regulated proteolysis in cells is conducted by the ubiquitin-proteasome system (UPS), in which proteins to be eliminated are selected through multiple steps to achieve high specificity. The large protease complex proteasome binds to ubiquitin molecules that are attached to the substrate and further interacts with a disordered region in the target to initiate unfolding for degradation. Recent studies have expanded our view of the complexity of ubiquitination as well as the details of substrate engagement by the proteasome and at the same time have suggested the characteristics of substrates that are susceptible to proteasomal degradation. Here, I review some destabilizing elements of proteasome substrates with particular attention to ubiquitination, initiation region and stability against unfolding and discuss their interplay to determine the substrate stability. A spatial perspective is important to understand the mechanism of action of proteasomal degradation, which may be critical for drug development targeting the UPS including targeted protein degradation.
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Žemeckienė, Živilė, Astra Vitkauskienė, Tatjana Sjakste, Brigita Šitkauskienė, and Raimundas Sakalauskas. "Proteasomes and Proteasomal Gene Polymorphism in Association with Inflammation and Various Diseases." Medicina 49, no. 5 (May 5, 2013): 33. http://dx.doi.org/10.3390/medicina49050033.
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A proteasome, a multicatalytic protein complex, is a central particle of the ubiquitinproteasome proteolytic pathway in all eukaryotic cells. Through the degradation of most intracellular proteins, proteasomes play a significant role in cell processes, such as cell cycle and division, posttranslational protein quality control, cell signaling, and apoptosis. Therefore, the ubiquitinproteasome system is necessary to ensure the normal functioning of cells and an organism. The associations between alterations in the ubiquitin-proteasome pathway and the development of various autoimmune, neurodegenerative, inflammatory and other diseases in humans have been established. Moreover, the findings of some studies suggest that proteasomes may participate in the pathogenesis of asthma through the regulation of the nuclear factor kappa B signaling pathway. Recently, much attention has been given to the associations between genes encoding the proteasome and their polymorphism, and various diseases. Associations between some proteasomal genes and myocardial infarction, type 2 diabetes mellitus, and other diseases have already been established. However, the results are inconclusive or conflicting and need further clarification.
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Boehringer, Jonas, Christiane Riedinger, Konstantinos Paraskevopoulos, Eachan O. D. Johnson, Edward D. Lowe, Christina Khoudian, Dominique Smith, Martin E. M. Noble, Colin Gordon, and Jane A. Endicott. "Structural and functional characterization of Rpn12 identifies residues required for Rpn10 proteasome incorporation." Biochemical Journal 448, no. 1 (October 18, 2012): 55–65. http://dx.doi.org/10.1042/bj20120542.
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The ubiquitin–proteasome system targets selected proteins for degradation by the 26S proteasome. Rpn12 is an essential component of the 19S regulatory particle and plays a role in recruiting the extrinsic ubiquitin receptor Rpn10. In the present paper we report the crystal structure of Rpn12, a proteasomal PCI-domain-containing protein. The structure helps to define a core structural motif for the PCI domain and identifies potential sites through which Rpn12 might form protein–protein interactions. We demonstrate that mutating residues at one of these sites impairs Rpn12 binding to Rpn10 in vitro and reduces Rpn10 incorporation into proteasomes in vivo.
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Buneeva, O. A., and A. E. Medvedev. "Ubiquitin-independent protein degradation in proteasomes." Biomeditsinskaya Khimiya 64, no. 2 (2018): 134–48. http://dx.doi.org/10.18097/pbmc20186402134.
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Proteasomes are large supramolecular protein complexes present in all prokaryotic and eukaryotic cells, where they perform targeted degradation of intracellular proteins. Until recently, it was generally accepted that prior proteolytic degradation in proteasomes the proteins had to be targeted by ubiquitination: the ATP-dependent addition of (typically four sequential) residues of the low-molecular ubiquitin protein, involving the ubiquitin-activating enzyme, ubiquitin-conjugating enzyme and ubiquitin ligase. The cytoplasm and nucleoplasm proteins labeled in this way are then digested in 26S proteasomes. However, in recent years it has become increasingly clear that using this route the cell eliminates only a part of unwanted proteins. Many proteins can be cleaved by the 20S proteasome in an ATP-independent manner and without previous ubiquitination. Ubiquitin-independent protein degradation in proteasomes is a relatively new area of studies of the role of the ubiquitin-proteasome system. However, recent data obtained in this direction already correct existing concepts about proteasomal degradation of proteins and its regulation. Ubiquitin-independent proteasome degradation needs the main structural precondition in proteins: the presence of unstructured regions in the amino acid sequences that provide interaction with the proteasome. Taking into consideration that in humans almost half of all genes encode proteins that contain a certain proportion of intrinsically disordered regions, it appears that the list of proteins undergoing ubiquitin-independent degradation will demonstrate further increase. Since 26S of proteasomes account for only 30% of the total proteasome content in mammalian cells, most of the proteasomes exist in the form of 20S complexes. The latter suggests that ubiquitin-independent proteolysis performed by the 20S proteasome is a natural process of removing damaged proteins from the cell and maintaining a constant level of intrinsically disordered proteins. In this case, the functional overload of proteasomes in aging and/or other types of pathological processes, if it is not accompanied by triggering more radical mechanisms for the elimination of damaged proteins, organelles and whole cells, has the most serious consequences for the whole organism.
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Asaka, Machiko, Tetsuaki Hirase, Aiko Hashimoto-Komatsu, and Koichi Node. "Rab5a-mediated localization of claudin-1 is regulated by proteasomes in endothelial cells." American Journal of Physiology-Cell Physiology 300, no. 1 (January 2011): C87—C96. http://dx.doi.org/10.1152/ajpcell.00565.2010.
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Tight junctions composed of transmembrane proteins, including claudin, occludin, and tricellulin, and peripheral membrane proteins are a major barrier to endothelial permeability, whereas the role of claudin in the regulation of tight junction permeability in nonneural endothelial cells is unclear. This study demonstrates that claudin-1 is dominantly expressed and depletion of claudin-1 using small interfering RNA (siRNA) increased tight junction permeability in EA hy.926 cells, indicating that claudin-1 is a crucial regulator of endothelial tight junction permeability. The ubiquitin-proteasome system has been implicated in the regulation of endocytotic trafficking of plasma membrane proteins. Therefore, the involvement of proteasomes in the localization of claudin-1 was investigated by pharmacological and genetic inhibition of proteasomes using a proteasome inhibitor, N-acetyl-Leu-Leu-Nle-CHO, and siRNA against the β5-subunit of the 20S proteasome, respectively. Claudin-1 was localized at cell-cell contact sites in control cells. Claudin-1 was localized in the cytoplasm in association with Rab5a and EEA-1, a marker of early endosome, following inhibition of proteasomes. Depletion of Rab5a using siRNA reversed the localization of claudin-1 induced by inhibition of proteasomes. These data suggest that proteasomes regulate claudin-1 localization at the plasma membrane, which changes upon proteasomal inhibition to a Rab5a-mediated endosomal localization.
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Magnani, Mauro. "Ubiquitin/proteasome system." Nature Biotechnology 18, no. 8 (August 2000): 807. http://dx.doi.org/10.1038/78325.
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Hilt, W., and D. H. Wolf. "Ubiquitin-proteasome system." Cellular and Molecular Life Sciences 61, no. 13 (June 2004): 1545. http://dx.doi.org/10.1007/s00018-004-4128-6.
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Hilt, W. "Ubiquitin-proteasome system." Cellular and Molecular Life Sciences 61, no. 13 (June 2004): 1615–32. http://dx.doi.org/10.1007/s00018-004-4135-7.
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DONOSO, Gerda, Volker HERZOG, and Anton SCHMITZ. "Misfolded BiP is degraded by a proteasome-independent endoplasmic-reticulum-associated degradation pathway." Biochemical Journal 387, no. 3 (April 26, 2005): 897–903. http://dx.doi.org/10.1042/bj20041312.
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Misfolded proteins are removed from the ER (endoplasmic reticulum) by retrotranslocation to the cytosol and degradation by the ubiquitin–proteasome system in a process designated ERAD (ER-associated degradation). Analysing the turnover of a misfolded form of the ER-resident chaperone BiP (heavy-chain binding protein) (BiPΔA), we found that the degradation of BiPΔA did not follow this general ERAD pathway. In transfected cells, BiPΔA was degraded, although proteasome-dependent ERAD was inactivated either by proteasome inhibitors or by ATP depletion. In semi-permeabilized cells, which did not support the degradation of the proteasomal substrate α1-antitrypsin, the degradation of BiPΔA was still functional, excluding the Golgi apparatus or lysosomes as the degradative compartment. The degradation of BiPΔA was recapitulated in biosynthetically loaded brain microsomes and in an extract of luminal ER proteins. In contrast with proteasome-dependent ERAD, degradation fragments were detectable inside the microsomes and in the extract, and the degradation was prevented by a serine protease inhibitor. These results show that the degradation of BiPΔA was initiated in the ER lumen by a serine protease, and support the view that proteasome-independent ERAD pathways exist.
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Akpinar, Kahraman, and Yaman. "Ochratoxin A Sequentially Activates Autophagy and the Ubiquitin-Proteasome System." Toxins 11, no. 11 (October 24, 2019): 615. http://dx.doi.org/10.3390/toxins11110615.
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Ochratoxin A (OTA) is a carcinogenic mycotoxin, which is produced by Aspergillus and Penicillium genera of fungi and commonly contaminates food and feed. We and others have previously shown that OTA causes sustained activation of PI3K/AKT and MAPK/ERK1-2 signaling pathways in different cell types and animal models. Given the close relationship between cellular signaling activity and protein stability, we were curious whether increased PI3K/AKT and MAPK/ERK1-2 signaling may be the result of OTA-stimulated alterations in proteolytic activity. We show that both of the major proteolytic systems, autophagy, and the ubiquitin-proteasome system (UPS), are activated upon OTA exposure in human kidney proximal tubule HK-2 and mouse embryonic fibroblast (MEF) cells. OTA stimulates transient autophagic activity at early time points of treatment but autophagic activity subsides after 6 h even in the sustained presence of OTA. Interestingly, OTA exposure also results in increased cell death in wild-type MEF cells but not in autophagy-halted Atg5-deficient cells, suggesting that autophagy exerts a pro-death effect on OTA-induced cytotoxicity. In addition, prolonged OTA exposure decreased ubiquitinated protein levels by increasing proteasomal activity. Using purified and cellular proteasomes, we observed enhanced chymotrypsin-, caspase-, and trypsin-like activities of the 26S but not the 20S proteasome in the presence of OTA. However, in the cellular context, increased proteasomal activity depended on prior induction of autophagy. Our results suggest that autophagy and subsequent UPS activation are responsible for sustained activation of PI3K/AKT and MAPK/ERK1-2 pathways through regulating the levels of critical phosphatases VHR/DUSP3, DUSP4, and PHLPP, which are known to be involved in OTA toxicity and carcinogenicity.
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Ding, Qunxing, and Jeffrey N. Keller. "Proteasomes and proteasome inhibition in the central nervous system." Free Radical Biology and Medicine 31, no. 5 (September 2001): 574–84. http://dx.doi.org/10.1016/s0891-5849(01)00635-9.
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Hu, Zongyi, Zhensheng Zhang, Edward Doo, Olivier Coux, Alfred L. Goldberg, and T. Jake Liang. "Hepatitis B Virus X Protein Is both a Substrate and a Potential Inhibitor of the Proteasome Complex." Journal of Virology 73, no. 9 (September 1, 1999): 7231–40. http://dx.doi.org/10.1128/jvi.73.9.7231-7240.1999.
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ABSTRACT The hepatitis B virus X protein (HBX) is essential for the establishment of HBV infection in vivo and exerts a pleiotropic effect on diverse cellular functions. The yeast two-hybrid system had indicated that HBX could interact with two subunits of the 26S proteasome. Here we demonstrate an association in vivo of HBX with the 26S proteasome complex by coimmunoprecipitation and colocalization upon sucrose gradient centrifugation. Expression of HBX in HepG2 cells caused a modest decrease in the proteasome’s chymotrypsin- and trypsin-like activities and in hydrolysis of ubiquitinated lysozyme, suggesting that HBX functions as an inhibitor of proteasome. In these cells, HBX is degraded with a half-life of 30 min. Proteasome inhibitors retarded this rapid degradation and caused a marked increase in the level of HBX and an accumulation of HBX in polyubiquitinated form. Thus, the low intracellular level of HBX is due to rapid proteolysis by the ubiquitin-proteasome pathway. Surprisingly, the proteasome inhibitors blocked the transactivation by HBX, and this effect was not a result of a squelching phenomenon due to HBX accumulation. Therefore, proteasome function is possibly required for the transactivation function of HBX. The inhibition of protein breakdown by proteasomes may account for the multiple actions of HBX and may be an important feature of HBV infection, possibly in helping stabilize viral gene products and suppressing antigen presentation.
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Dron, Michel, Françoise Dandoy-Dron, Muhammad Khalid Farooq Salamat, and Hubert Laude. "Proteasome inhibitors promote the sequestration of PrPSc into aggresomes within the cytosol of prion-infected CAD neuronal cells." Journal of General Virology 90, no. 8 (August 1, 2009): 2050–60. http://dx.doi.org/10.1099/vir.0.010082-0.
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Dysfunction of the endoplasmic reticulum associated protein degradation/proteasome system is believed to contribute to the initiation or aggravation of neurodegenerative disorders associated with protein misfolding, and there is some evidence to suggest that proteasome dysfunctions might be implicated in prion disease. This study investigated the effect of proteasome inhibitors on the biogenesis of both the cellular (PrPC) and abnormal (PrPSc) forms of prion protein in CAD neuronal cells, a newly introduced prion cell system. In uninfected cells, proteasome impairment altered the intracellular distribution of PrPC, leading to a strong accumulation in the Golgi apparatus. Moreover, a detergent-insoluble and weakly protease-resistant PrP species of 26 kDa, termed PrP26K, accumulated in the cells, whether they were prion-infected or not. However, no evidence was found that, in infected cells, this PrP26K species converts into the highly proteinase K-resistant PrPSc. In the infected cultures, proteasome inhibition caused an increased intracellular aggregation of PrPSc that was deposited into large aggresomes. These findings strengthen the view that, in neuronal cells expressing wild-type PrPC from the natural promoter, proteasomal impairment may affect both the process of PrPC biosynthesis and the subcellular sites of PrPSc accumulation, despite the fact that these two effects could essentially be disconnected.
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Ma, Wanlong, Hagop M. Kantarjian, XI Zhang, Xiuqiang Wang, Zeev Estrov, Susan O'Brien, and Maher Albitar. "Clinical Relevance of Ubiquitin-Proteasome System Profiling in Acute Leukemias." Blood 114, no. 22 (November 20, 2009): 2633. http://dx.doi.org/10.1182/blood.v114.22.2633.2633.
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Abstract Abstract 2633 Poster Board II-609 The ubiquitin-proteasome system (UPS) plays a major role in the homeostasis of cellular proteins: chymotrypsin-like (Ch-L), caspase-like (Cas-L), and trypsin-like (Tr-L). The UPS system is involved in most critical cellular processes and its role in oncogenesis is well established. Here we compared UPS protein levels (proteasome and ubiquitin) and proteasome enzymatic activities in peripheral blood plasma from newly diagnosed patients with acute myeloid leukemia (AML; n=147), acute lymphoblastic leukemia (ALL; n=34?), or myelodysplastic syndrome (MDS ; n=27), and 99 apparently healthy control subjects. Proteasome and ubiquitin were measured using immunoassays based on electro-chemiluminescence technology. The proteasome enzymatic activities were measure using a standard enzymatic assay utilizing fluorogenic peptide-AMC substrate. By normalizing these enzymatic activities to the levels of proteasome protein in plasma, we also determined specific proteasome enzyme activities (Ch-L/p, Cas-L/p, and Tr-L, respectively). AML, ALL, and MDS patients all had high levels of proteasome protein, ubiquitin, and enzymatic activities relative to control subjects. However, each specific enzyme activity in general was lower in all 3 disease groups than in control subjects, which suggests that each proteasome has lower enzymatic activity in blast cells but we cannot rule out that the number of proteasomes might be increased. Despite these similarities, AML, ALL, and MDS each exhibited a specific profile of UPS protein and enzymatic activities . Proteasome protein levels and enzymatic activities also correlated with clinical behavior. In AML, proteasome protein level was a strong predictor of survival as a both a continuous (P<0.00001) and a dichotomous (P=0.04) variable, independent of cytogenetics, performance status, and age. In ALL, Ch-L/p showed a significant negative correlation with survival (P=0.0015). In conclusion, these data demonstrate that each disease has a unique UPS profile and confirm that the UPS system plays a major role in the leukemic process. In addition, profiling the UPS in leukemias using plasma provides valuable biomarkers that can be used to help predict clinical behavior and may ultimately help manage disease. Disclosures: No relevant conflicts of interest to declare.
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Scott, Craig M., Kristina B. Kruse, Béla Z. Schmidt, David H. Perlmutter, Ardythe A. McCracken, and Jeffrey L. Brodsky. "ADD66, a Gene Involved in the Endoplasmic Reticulum-associated Degradation of α-1-Antitrypsin-Z in Yeast, Facilitates Proteasome Activity and Assembly." Molecular Biology of the Cell 18, no. 10 (October 2007): 3776–87. http://dx.doi.org/10.1091/mbc.e07-01-0034.
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Antitrypsin deficiency is a primary cause of juvenile liver disease, and it arises from expression of the “Z” variant of the α-1 protease inhibitor (A1Pi). Whereas A1Pi is secreted from the liver, A1PiZ is retrotranslocated from the endoplasmic reticulum (ER) and degraded by the proteasome, an event that may offset liver damage. To better define the mechanism of A1PiZ degradation, a yeast expression system was developed previously, and a gene, ADD66, was identified that facilitates A1PiZ turnover. We report here that ADD66 encodes an ∼30-kDa soluble, cytosolic protein and that the chymotrypsin-like activity of the proteasome is reduced in add66Δ mutants. This reduction in activity may arise from the accumulation of 20S proteasome assembly intermediates or from qualitative differences in assembled proteasomes. Add66p also seems to be a proteasome substrate. Consistent with its role in ER-associated degradation (ERAD), synthetic interactions are observed between the genes encoding Add66p and Ire1p, a transducer of the unfolded protein response, and yeast deleted for both ADD66 and/or IRE1 accumulate polyubiquitinated proteins. These data identify Add66p as a proteasome assembly chaperone (PAC), and they provide the first link between PAC activity and ERAD.
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Xolalpa, Wendy, Patricia Perez-Galan, Manuel S. Rodríguez, and Gael Roue. "Targeting the Ubiquitin Proteasome System: Beyond Proteasome Inhibition." Current Pharmaceutical Design 19, no. 22 (May 1, 2013): 4053–93. http://dx.doi.org/10.2174/1381612811319220014.
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Buneeva, O. A., A. T. Kopylov, V. G. Zgoda, O. V. Gnedenko, S. A. Kaloshina, M. V. Medvedeva, A. S. Ivanov, and A. E. Medvedev. "Comparative analysis of proteins associated with 26S and 20S proteasomes isolated from rabbit brain and liver." Biomeditsinskaya Khimiya 68, no. 1 (2022): 18–31. http://dx.doi.org/10.18097/pbmc20226801018.
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We have isolated fractions of 26S and 20S proteasomes were from the rabbit liver and the brain. According to mass spectrometric (MS) analysis, the 26S proteasome fractions from these organs contained catalytic and regulatory subunits characteristic of the proteasome core and regulatory subunits. The 20S fractions of brain and liver proteasomes contained only catalytic proteasome subunits. In addition to proteasome subunits, the isolated fractions contained components of the ubiquitin-proteasome system, ubiquitinated proteins, enzymes that play an important role in metabolic processes, cytoskeletal components, signaling, regulatory, and protective proteins, as well as proteins regulating gene expression, cell division, and differentiation. The abundance of a number of proteasome-associated proteins was comparable or exceeded the abundance of intrinsic proteasome components. About a third of the proteins common to all studied fractions (26S and 20S of brain and liver proteasomes) belong to the group of multifunctional proteins. Selective biosensor validation confirmed the affinity binding of proteins (aldolase, phosphoglycerate kinase) identified during MS analysis to the brain 20S proteasome. Comparison of the subproteomes of the 26S and 20S brain proteasomes showed that removal of components of the regulatory (19S) subparticles caused almost two-fold increase in the total number of individual proteins associated with the core part of the proteasome (20S). In the liver, the number of proteins associated with the core part of the proteasome remained basically unchanged after the removal of the components of the regulatory (19S) subparticles. This indicates that in the brain and, possibly, in other organs, proteins of the regulatory (19S) subunit play an important role in the formation of the proteasome interactome.
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Seifert, Ulrike, and Elke Krüger. "Remodelling of the ubiquitin–proteasome system in response to interferons." Biochemical Society Transactions 36, no. 5 (September 19, 2008): 879–84. http://dx.doi.org/10.1042/bst0360879.
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Peptide generation by the UPS (ubiquitin–proteasome system) is rate-limiting in MHC class I-restricted antigen presentation in response to virus-induced IFNs (interferons). In this process, the role of IFN-induced rapid remodelling of the UPS is less defined. IFN-mediated de novo formation of different proteasome compositions as i20S (immunoproteasomes) or m20S (mixed-type proteasomes) essentially supports the rapid adjustment of the mammalian immune system to pathogens. This adjustment is of particular importance for the immune response to rapidly replicating viruses. In agreement, i20S formation has been shown to be an accelerated and transient response. Moreover, i20S and/or PA28 (proteasome activator 28) are essentially required for the generation of certain viral epitopes. In the present paper, we discuss how IFNs consecutively regulate the UPS at different levels, thereby improving the immune responsiveness of target cells.
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Niedermann, Gabriele, Rudolf Grimm, Elke Geier, Martina Maurer, Claudio Realini, Christoph Gartmann, Jürgen Soll, et al. "Potential Immunocompetence of Proteolytic Fragments Produced by Proteasomes before Evolution of the Vertebrate Immune System." Journal of Experimental Medicine 186, no. 2 (July 21, 1997): 209–20. http://dx.doi.org/10.1084/jem.186.2.209.
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To generate peptides for presentation by major histocompatibility complex (MHC) class I molecules to T lymphocytes, the immune system of vertebrates has recruited the proteasomes, phylogenetically ancient multicatalytic high molecular weight endoproteases. We have previously shown that many of the proteolytic fragments generated by vertebrate proteasomes have structural features in common with peptides eluted from MHC class I molecules, suggesting that many MHC class I ligands are direct products of proteasomal proteolysis. Here, we report that the processing of polypeptides by proteasomes is conserved in evolution, not only among vertebrate species, but including invertebrate eukaryotes such as insects and yeast. Unexpectedly, we found that several high copy ligands of MHC class I molecules, in particular, self-ligands, are major products in digests of source polypeptides by invertebrate proteasomes. Moreover, many major dual cleavage peptides produced by invertebrate proteasomes have the length and the NH2 and COOH termini preferred by MHC class I. Thus, the ability of proteasomes to generate potentially immunocompetent peptides evolved well before the vertebrate immune system. We demonstrate with polypeptide substrates that interferon γ induction in vivo or addition of recombinant proteasome activator 28α in vitro alters proteasomal proteolysis in such a way that the generation of peptides with the structural features of MHC class I ligands is optimized. However, these changes are quantitative and do not confer qualitatively novel characteristics to proteasomal proteolysis. The data suggest that proteasomes may have influenced the evolution of MHC class I molecules.
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Tsimokha, Anna S., Tatiana O. Artamonova, Egor E. Diakonov, Mikhail A. Khodorkovskii, and Alexey N. Tomilin. "Post-Translational Modifications of Extracellular Proteasome." Molecules 25, no. 15 (July 31, 2020): 3504. http://dx.doi.org/10.3390/molecules25153504.
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The ubiquitin-proteasome system (UPS) is one of the major protein degradation pathways in eukaryotic cells. Abnormal functioning of this system has been observed in cancer and neurological diseases. The 20S proteasomes, essential components of the UPS, are present not only within the cells but also in the extracellular space, and their concentration in blood plasma has been found to be elevated and dependent upon the disease state, being of prognostic significance in patients suffering from cancer, liver diseases, and autoimmune diseases. However, functions of extracellular proteasomes and mechanisms of their release by cells remain largely unknown. The main mechanism of proteasome activity regulation is provided by modulation of their composition and post-translational modifications (PTMs). Moreover, diverse PTMs of proteins are known to participate in the loading of specific elements into extracellular vesicles. Since previous studies have revealed that the transport of extracellular proteasomes may occur via extracellular vesicles, we have set out to explore the PTMs of extracellular proteasomes in comparison to cellular counterparts. In this work, cellular and extracellular proteasomes were affinity purified and separated by SDS-PAGE for subsequent trypsinization and matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) analysis. In total, we could identify 64 and 55 PTM sites in extracellular and cellular proteasomes, respectively, including phosphorylation, ubiquitination, acetylation, and succinylation. We observed novel sites of acetylation at K238 and K192 of the proteasome subunits β2 and β3, respectively, that are specific for extracellular proteasomes. Moreover, cellular proteasomes show specific acetylation at K227 of α2 and ubiquitination at K201 of β3. Interestingly, succinylation of β6 at the residue K228 seems not to be present exclusively in extracellular proteasomes, whereas both extracellular and cellular proteasomes may also be acetylated at this site. The same situation takes place at K201 of the β3 subunit where ubiquitination is seemingly specific for cellular proteasomes. Moreover, crosstalk between acetylation, ubiquitination, and succinylation has been observed in the subunit α3 of both proteasome populations. These data will serve as a basis for further studies, aimed at dissection of the roles of extracellular proteasome-specific PTMs in terms of the function of these proteasomes and mechanism of their transport into extracellular space.
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Jannuzzi, Ayse Tarbin, Gulce Sari, Ayse Mine Yilmaz, Betul Karademir, and Buket Alpertunga. "Proteasomal Inhibition with Bortezomib Causes Selective Autophagy Upregulation and Perinuclear Clustering of Mitochondria in Human Neuronal Cells." Proceedings 2, no. 25 (December 6, 2018): 1583. http://dx.doi.org/10.3390/proceedings2251583.
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The ubiquitin proteasomal system and autophagic pathway are two main protein degradation systems in eukaryotic cells. Inhibition of the proteasomal system with proteasome inhibitors for cancer treatment can cause neurotoxic side effects. In this study, we investigated neurotoxic side effects of bortezomib (BTZ) and carfilzomib (CFZ) in a human neuronal cell model. Inhibition of proteasome with BTZ upregulated autophagy receptor protein p62 level. BTZ caused reduced mitochondrial mass per cell in a greater extent than CFZ. BTZ caused more clustering of mitochondria than CFZ. In conclusion, mitochondrial toxicity and autophagic upregulation with BTZ may be the reason for more severe neurotoxic profile than CFZ.
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Teale, Alastair, Stephanie Campbell, Nick Van Buuren, Wendy C. Magee, Kelly Watmough, Brianne Couturier, Robyn Shipclark, and Michele Barry. "Orthopoxviruses Require a Functional Ubiquitin-Proteasome System for Productive Replication." Journal of Virology 83, no. 5 (December 24, 2008): 2099–108. http://dx.doi.org/10.1128/jvi.01753-08.
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ABSTRACT Cellular homeostasis depends on an intricate balance of protein expression and degradation. The ubiquitin-proteasome pathway plays a crucial role in specifically targeting proteins tagged with ubiquitin for destruction. This degradation can be effectively blocked by both chemically synthesized and natural proteasome inhibitors. Poxviruses encode a number of proteins that exploit the ubiquitin-proteasome system, including virally encoded ubiquitin molecules and ubiquitin ligases, as well as BTB/kelch proteins and F-box proteins, which interact with cellular ubiquitin ligases. Here we show that poxvirus infection was dramatically affected by a range of proteasome inhibitors, including MG132, MG115, lactacystin, and bortezomib (Velcade). Confocal microscopy demonstrated that infected cells treated with MG132 or bortezomib lacked viral replication factories within the cytoplasm. This was accompanied by the absence of late gene expression and DNA replication; however, early gene expression occurred unabated. Proteasomal inhibition with MG132 or bortezomib also had dramatic effects on viral titers, severely blocking viral replication and propagation. The effects of MG132 on poxvirus infection were reversible upon washout, resulting in the production of late genes and viral replication factories. Significantly, the addition of an ubiquitin-activating enzyme (E1) inhibitor had a similar affect on late and early protein expression. Together, our data suggests that a functional ubiquitin-proteasome system is required during poxvirus infection.
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Masdehors, Peggy, Hélène Merle-Béral, Karim Maloum, Satoshi Ömura, Henri Magdelénat, and Jozo Delic. "Deregulation of the ubiquitin system and p53 proteolysis modify the apoptotic response in B-CLL lymphocytes." Blood 96, no. 1 (July 1, 2000): 269–74. http://dx.doi.org/10.1182/blood.v96.1.269.
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Abstract We recently reported increased sensitivity of B-cell chronic lymphocytic leukemia (B-CLL) lymphocytes to apoptotic death activation by the proteasome-specific inhibitor lactacystin. Here, we show that only specific—not nonspecific—proteasomal inhibitors can discriminate between malignant and normal lymphocytes in inducing the apoptotic death response. Indeed, lactacystin and its active metaboliteclasto-lactacystin β-lactone induced apoptotic death in CLL but not in normal lymphocytes. This difference was completely abolished when tripeptide aldehydes such as MG132 or LLnL (which can also inhibit calpains) were used as less specific proteasomal inhibitors. Moreover, B-CLL cells exhibited a constitutive altered ubiquitin-proteasome system, including a threefold higher chymotrypsin-like proteasomal activity and high levels of nuclear ubiquitin-conjugated proteins compared with normal lymphocytes. Interestingly, B-CLL cells also displayed altered proteolytic regulation of wild-type p53, an apoptotic factor reported to be a substrate for the ubiquitin-proteasome system. Nuclear wild-type p53 accumulated after lactacystin treatment used at the discriminating concentration in malignant, but not in normal, lymphocytes. In contrast, p53 was stabilized by MG132 or LLnL in malignant and normal cells undergoing apoptosis, indicating that in normal lymphocytes p53 is regulated mainly by calpains and not by the ubiquitin-proteasome system. This work raises the possibility that two different proteolytic pathways controlling p53 stability may be pathologically imbalanced. This could result in modification of apoptosis control, since in CLL-lymphocytes a highly upregulated ubiquitin-proteasome system, which controls p53 stability among other apoptotic factors, was correlated with an increased propensity of these cells to apoptosis triggered by lactacystin.
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Masdehors, Peggy, Hélène Merle-Béral, Karim Maloum, Satoshi Ömura, Henri Magdelénat, and Jozo Delic. "Deregulation of the ubiquitin system and p53 proteolysis modify the apoptotic response in B-CLL lymphocytes." Blood 96, no. 1 (July 1, 2000): 269–74. http://dx.doi.org/10.1182/blood.v96.1.269.013k10_269_274.
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We recently reported increased sensitivity of B-cell chronic lymphocytic leukemia (B-CLL) lymphocytes to apoptotic death activation by the proteasome-specific inhibitor lactacystin. Here, we show that only specific—not nonspecific—proteasomal inhibitors can discriminate between malignant and normal lymphocytes in inducing the apoptotic death response. Indeed, lactacystin and its active metaboliteclasto-lactacystin β-lactone induced apoptotic death in CLL but not in normal lymphocytes. This difference was completely abolished when tripeptide aldehydes such as MG132 or LLnL (which can also inhibit calpains) were used as less specific proteasomal inhibitors. Moreover, B-CLL cells exhibited a constitutive altered ubiquitin-proteasome system, including a threefold higher chymotrypsin-like proteasomal activity and high levels of nuclear ubiquitin-conjugated proteins compared with normal lymphocytes. Interestingly, B-CLL cells also displayed altered proteolytic regulation of wild-type p53, an apoptotic factor reported to be a substrate for the ubiquitin-proteasome system. Nuclear wild-type p53 accumulated after lactacystin treatment used at the discriminating concentration in malignant, but not in normal, lymphocytes. In contrast, p53 was stabilized by MG132 or LLnL in malignant and normal cells undergoing apoptosis, indicating that in normal lymphocytes p53 is regulated mainly by calpains and not by the ubiquitin-proteasome system. This work raises the possibility that two different proteolytic pathways controlling p53 stability may be pathologically imbalanced. This could result in modification of apoptosis control, since in CLL-lymphocytes a highly upregulated ubiquitin-proteasome system, which controls p53 stability among other apoptotic factors, was correlated with an increased propensity of these cells to apoptosis triggered by lactacystin.
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Sommer, Thomas, and Dieter H. Wolf. "The ubiquitin–proteasome-system." Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 1843, no. 1 (January 2014): 1. http://dx.doi.org/10.1016/j.bbamcr.2013.09.009.
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Nandi, Dipankar, Pankaj Tahiliani, Anujith Kumar, and Dilip Chandu. "The ubiquitin-proteasome system." Journal of Biosciences 31, no. 1 (March 2006): 137–55. http://dx.doi.org/10.1007/bf02705243.
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Shah, Imtiaz, and Mario Napoli. "The Ubiquitin-Proteasome System and Proteasome Inhibitors in Central Nervous System Diseases." Cardiovascular & Hematological Disorders-Drug Targets 7, no. 4 (December 1, 2007): 250–73. http://dx.doi.org/10.2174/187152907782793572.
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Goetzke, Carl Christoph, Frédéric Ebstein, and Tilmann Kallinich. "Role of Proteasomes in Inflammation." Journal of Clinical Medicine 10, no. 8 (April 20, 2021): 1783. http://dx.doi.org/10.3390/jcm10081783.
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The ubiquitin–proteasome system (UPS) is involved in multiple cellular functions including the regulation of protein homeostasis, major histocompatibility (MHC) class I antigen processing, cell cycle proliferation and signaling. In humans, proteasome loss-of-function mutations result in autoinflammation dominated by a prominent type I interferon (IFN) gene signature. These genomic alterations typically cause the development of proteasome-associated autoinflammatory syndromes (PRAAS) by impairing proteasome activity and perturbing protein homeostasis. However, an abnormal increased proteasomal activity can also be found in other human inflammatory diseases. In this review, we cast a light on the different clinical aspects of proteasomal activity in human disease and summarize the currently studied therapeutic approaches.
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Bai, Lin, Kuan Hu, Tong Wang, Jordan B. Jastrab, K. Heran Darwin, and Huilin Li. "Structural analysis of the dodecameric proteasome activator PafE in Mycobacterium tuberculosis." Proceedings of the National Academy of Sciences 113, no. 14 (March 21, 2016): E1983—E1992. http://dx.doi.org/10.1073/pnas.1512094113.
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The human pathogen Mycobacterium tuberculosis (Mtb) requires a proteasome system to cause lethal infections in mice. We recently found that proteasome accessory factor E (PafE, Rv3780) activates proteolysis by the Mtb proteasome independently of adenosine triphosphate (ATP). Moreover, PafE contributes to the heat-shock response and virulence of Mtb. Here, we show that PafE subunits formed four-helix bundles similar to those of the eukaryotic ATP-independent proteasome activator subunits of PA26 and PA28. However, unlike any other known proteasome activator, PafE formed dodecamers with 12-fold symmetry, which required a glycine-XXX-glycine-XXX-glycine motif that is not found in previously described activators. Intriguingly, the truncation of the PafE carboxyl-terminus resulted in the robust binding of PafE rings to native proteasome core particles and substantially increased proteasomal activity, suggesting that the extended carboxyl-terminus of this cofactor confers suboptimal binding to the proteasome core particle. Collectively, our data show that proteasomal activation is not limited to hexameric ATPases in bacteria.
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van Rijt, Sabine H., Ilona E. Keller, Gerrit John, Kathrin Kohse, Ali Ö. Yildirim, Oliver Eickelberg, and Silke Meiners. "Acute cigarette smoke exposure impairs proteasome function in the lung." American Journal of Physiology-Lung Cellular and Molecular Physiology 303, no. 9 (November 1, 2012): L814—L823. http://dx.doi.org/10.1152/ajplung.00128.2012.
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Cigarette smoke mediates DNA damage, lipid peroxidation, and modification and misfolding of proteins, thereby inducing severe cellular damage. The ubiquitin proteasome system serves as the major disposal system for modified and misfolded proteins and is thus essential for proper cellular function. Its role in cigarette smoke-induced cell damage, however, is largely unknown. We hypothesized that the ubiquitin-proteasome system is involved in the degradation of cigarette smoke-damaged proteins and that cigarette smoke exposure impairs the proteasome itself. Here, we show that treatment of human alveolar epithelial cells with cigarette smoke extract (CSE) induced time- and dose-dependent cell death, a rise in intracellular reactive oxygen species, and increased levels of carbonylated and polyubiquitinated proteins. While high doses of CSE severely impaired all three proteasomal activities, low CSE concentrations significantly inhibited only the trypsin-like activity of the proteasome in alveolar and bronchial epithelial cells. Moreover, acute exposure of mice to cigarette smoke significantly impaired the trypsin-like activity by 25% in the lungs. Reduced proteasome activity was not due to transcriptional regulation of the proteasome. Notably, cigarette smoke exposure induced accumulation of polyubiquitinated proteins in the soluble and insoluble protein fraction of the lung. We show for the first time that acute exposure to cigarette smoke directly impairs proteasome activity in the lungs of mice and in human epithelial cells at low doses without affecting proteasome expression. Our results indicate that defective proteasomal protein quality control may exacerbate the detrimental effects of cigarette smoke in the lung.
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Ghaboosi, Nazli, and Raymond J. Deshaies. "A Conditional Yeast E1 Mutant Blocks the Ubiquitin–Proteasome Pathway and Reveals a Role for Ubiquitin Conjugates in Targeting Rad23 to the Proteasome." Molecular Biology of the Cell 18, no. 5 (May 2007): 1953–63. http://dx.doi.org/10.1091/mbc.e06-10-0965.
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E1 ubiquitin activating enzyme catalyzes the initial step in all ubiquitin-dependent processes. We report the isolation of uba1-204, a temperature-sensitive allele of the essential Saccharomyces cerevisiae E1 gene, UBA1. Uba1-204 cells exhibit dramatic inhibition of the ubiquitin–proteasome system, resulting in rapid depletion of cellular ubiquitin conjugates and stabilization of multiple substrates. We have employed the tight phenotype of this mutant to investigate the role ubiquitin conjugates play in the dynamic interaction of the UbL/UBA adaptor proteins Rad23 and Dsk2 with the proteasome. Although proteasomes purified from mutant cells are intact and proteolytically active, they are depleted of ubiquitin conjugates, Rad23, and Dsk2. Binding of Rad23 to these proteasomes in vitro is enhanced by addition of either free or substrate-linked ubiquitin chains. Moreover, association of Rad23 with proteasomes in mutant and wild-type cells is improved upon stabilizing ubiquitin conjugates with proteasome inhibitor. We propose that recognition of polyubiquitin chains by Rad23 promotes its shuttling to the proteasome in vivo.
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Zhao, Jinghui, Bo Zhai, Steven P. Gygi, and Alfred Lewis Goldberg. "mTOR inhibition activates overall protein degradation by the ubiquitin proteasome system as well as by autophagy." Proceedings of the National Academy of Sciences 112, no. 52 (December 15, 2015): 15790–97. http://dx.doi.org/10.1073/pnas.1521919112.
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Growth factors and nutrients enhance protein synthesis and suppress overall protein degradation by activating the protein kinase mammalian target of rapamycin (mTOR). Conversely, nutrient or serum deprivation inhibits mTOR and stimulates protein breakdown by inducing autophagy, which provides the starved cells with amino acids for protein synthesis and energy production. However, it is unclear whether proteolysis by the ubiquitin proteasome system (UPS), which catalyzes most protein degradation in mammalian cells, also increases when mTOR activity decreases. Here we show that inhibiting mTOR with rapamycin or Torin1 rapidly increases the degradation of long-lived cell proteins, but not short-lived ones, by stimulating proteolysis by proteasomes, in addition to autophagy. This enhanced proteasomal degradation required protein ubiquitination, and within 30 min after mTOR inhibition, the cellular content of K48-linked ubiquitinated proteins increased without any change in proteasome content or activity. This rapid increase in UPS-mediated proteolysis continued for many hours and resulted primarily from inhibition of mTORC1 (not mTORC2), but did not require new protein synthesis or key mTOR targets: S6Ks, 4E-BPs, or Ulks. These findings do not support the recent report that mTORC1 inhibition reduces proteolysis by suppressing proteasome expression [Zhang Y, et al. (2014) Nature 513(7518):440–443]. Several growth-related proteins were identified that were ubiquitinated and degraded more rapidly after mTOR inhibition, including HMG-CoA synthase, whose enhanced degradation probably limits cholesterol biosynthesis upon insulin deficiency. Thus, mTOR inhibition coordinately activates the UPS and autophagy, which provide essential amino acids and, together with the enhanced ubiquitination of anabolic proteins, help slow growth.
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Choi, Won Hoon, Yejin Yun, Seoyoung Park, Jun Hyoung Jeon, Jeeyoung Lee, Jung Hoon Lee, Su-A. Yang, et al. "Aggresomal sequestration and STUB1-mediated ubiquitylation during mammalian proteaphagy of inhibited proteasomes." Proceedings of the National Academy of Sciences 117, no. 32 (July 28, 2020): 19190–200. http://dx.doi.org/10.1073/pnas.1920327117.
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The 26S proteasome, a self-compartmentalized protease complex, plays a crucial role in protein quality control. Multiple levels of regulatory systems modulate proteasomal activity for substrate hydrolysis. However, the destruction mechanism of mammalian proteasomes is poorly understood. We found that inhibited proteasomes are sequestered into the insoluble aggresome via HDAC6- and dynein-mediated transport. These proteasomes colocalized with the autophagic receptor SQSTM1 and cleared through selective macroautophagy, linking aggresomal segregation to autophagic degradation. This proteaphagic pathway was counterbalanced with the recovery of proteasomal activity and was critical for reducing cellular proteasomal stress. Changes in associated proteins and polyubiquitylation on inhibited 26S proteasomes participated in the targeting mechanism to the aggresome and autophagosome. The STUB1 E3 Ub ligase specifically ubiquitylated purified human proteasomes in vitro, mainly via Lys63-linked chains. Genetic and chemical inhibition of STUB1 activity significantly impaired proteasome processing and reduced resistance to proteasomal stress. These data demonstrate that aggresomal sequestration is the crucial upstream event for proteasome quality control and overall protein homeostasis in mammals.
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Sari, Gulce, Zehra Okat, Ali Sahin, and Betul Karademir. "Proteasome Inhibitors in Cancer Therapy and their Relation to Redox Regulation." Current Pharmaceutical Design 24, no. 44 (March 29, 2019): 5252–67. http://dx.doi.org/10.2174/1381612825666190201120013.
Full textAbstract:
Redox homeostasis is important for the maintenance of cell survival. Under physiological conditions, redox system works in a balance and involves activation of many signaling molecules. Regulation of redox balance via signaling molecules is achieved by different pathways and proteasomal system is a key pathway in this process. Importance of proteasomal system on signaling pathways has been investigated for many years. In this direction, many proteasome targeting molecules have been developed. Some of them are already in the clinic for cancer treatment and some are still under investigation to highlight underlying mechanisms. Although there are many studies done, molecular mechanisms of proteasome inhibitors and related signaling pathways need more detailed explanations. This review aims to discuss redox status and proteasomal system related signaling pathways. In addition, cancer therapies targeting proteasomal system and their effects on redox-related pathways have been summarized.
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George, Dare E., and Jetze J. Tepe. "Advances in Proteasome Enhancement by Small Molecules." Biomolecules 11, no. 12 (November 30, 2021): 1789. http://dx.doi.org/10.3390/biom11121789.
Full textAbstract:
The proteasome system is a large and complex molecular machinery responsible for the degradation of misfolded, damaged, and redundant cellular proteins. When proteasome function is impaired, unwanted proteins accumulate, which can lead to several diseases including age-related and neurodegenerative diseases. Enhancing proteasome-mediated substrate degradation with small molecules may therefore be a valuable strategy for the treatment of various neurodegenerative diseases such as Parkinson’s, Alzheimer’s, and Huntington’s diseases. In this review, we discuss the structure of proteasome and how proteasome’s proteolytic activity is associated with aging and various neurodegenerative diseases. We also summarize various classes of compounds that are capable of enhancing, directly or indirectly, proteasome-mediated protein degradation.