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Trends in Genetics : TIG Feb 2021The key to a healthy mammalian cell lies in properly functioning proteolytic machineries called proteasomes. The proteasomes are multisubunit complexes that catalyze the... (Review)
Review
The key to a healthy mammalian cell lies in properly functioning proteolytic machineries called proteasomes. The proteasomes are multisubunit complexes that catalyze the degradation of unwanted proteins and also control half-lives of key cellular regulatory factors. Aberrant proteasome activity is often associated with human diseases such as cancer and neurodegeneration, and so an in-depth understanding of how it is regulated has implications for potential disease interventions. Transcriptional regulation of the proteasome can dictate its abundance and also influence its function, assembly, and location. This ensures proper proteasomal activity in response to developmental cues and to physiological conditions such as starvation and oxidative stress. In this review, we highlight and discuss the roles of the transcription factors that are involved in the regulation of the mammalian proteasome.
Topics: Animals; Humans; Mammals; Neoplasms; Oxidative Stress; Proteasome Endopeptidase Complex; Proteins; Proteolysis; Transcription Factors; Transcription, Genetic
PubMed: 32988635
DOI: 10.1016/j.tig.2020.09.005 -
BMB Reports Apr 2022The mechanistic target of rapamycin (mTOR) regulates numerous extracellular and intracellular signals involved in the maintenance of cellular homeostasis and cell...
The mechanistic target of rapamycin (mTOR) regulates numerous extracellular and intracellular signals involved in the maintenance of cellular homeostasis and cell growth. mTOR also functions as an endogenous inhibitor of autophagy. Under nutrient-rich conditions, mTOR complex 1 (mTORC1) phosphorylates the ULK1 complex, preventing its activation and subsequent autophagosome formation, while inhibition of mTORC1 using either rapamycin or nutrient deprivation induces autophagy. Autophagy and proteasomal proteolysis provide amino acids necessary for protein translation. Although the connection between mTORC1 and autophagy is well characterized, the association of mTORC1 inhibition with proteasome biogenesis and activity has not been fully elucidated yet. Proteasomes are long-lived cellular organelles. Their spatiotemporal rather than homeostatic regulation could be another adaptive cellular mechanism to respond to starvation. Here, we reviewed several published reports and the latest research from our group to examine the connection between mTORC1 and proteasome. We have also investigated and described the effect of mTORC1 inhibition on proteasome activity using purified proteasomes. Since mTORC1 inhibitors are currently evaluated as treatments for several human diseases, a better understanding of the link between mTORC1 activity and proteasome function is of utmost importance. [BMB Reports 2022; 55(4): 161-165].
Topics: Autophagy; Autophagy-Related Protein-1 Homolog; Humans; Mechanistic Target of Rapamycin Complex 1; Proteasome Endopeptidase Complex; Sirolimus; TOR Serine-Threonine Kinases
PubMed: 35321785
DOI: 10.5483/BMBRep.2022.55.4.032 -
The Journal of Biological Chemistry Nov 2022The REGγ-20S proteasome is an ubiquitin- and ATP-independent degradation system, targeting selective substrates, possibly helping to regulate aging. The studies we...
The REGγ-20S proteasome is an ubiquitin- and ATP-independent degradation system, targeting selective substrates, possibly helping to regulate aging. The studies we report here demonstrate that aging-associated REGγ decline predisposes to decreasing tau turnover, as in a tauopathy. The REGγ proteasome promotes degradation of human and mouse tau, notably phosphorylated tau and toxic tau oligomers that shuttle between the cytoplasm and nuclei. REGγ-mediated proteasomal degradation of tau was validated in 3- to 12-month-old REGγ KO mice, REGγ KO;PS19 mice, and PS19 mice with forebrain conditional neuron-specific overexpression of REGγ (REGγ OE) and behavioral abnormalities. Coupled with tau accumulation, we found with REGγ-deficiency, neuron loss, dendrite reduction, tau filament accumulation, and microglial activation are much more prominent in the REGγ KO;PS19 than the PS19 model. Moreover, we observed that the degenerative neuronal lesions and aberrant behaviors were alleviated in REGγ OE;PS19 mice. Memory and other behavior analysis substantiate the role of REGγ in prevention of tauopathy-like symptoms. In addition, we investigated the potential mechanism underlying aging-related REGγ decline. This study provides valuable insights into the novel regulatory mechanisms and potential therapeutic targets for tau-related neurodegenerative diseases.
Topics: Humans; Animals; Mice; Infant; Proteasome Endopeptidase Complex; Tauopathies; Autoantigens; Cytoplasm; Aging
PubMed: 36209822
DOI: 10.1016/j.jbc.2022.102571 -
Current Pharmaceutical Design 2018Redox homeostasis is important for the maintenance of cell survival. Under physiological conditions, redox system works in a balance and involves activation of many... (Review)
Review
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.
Topics: Animals; Cell Survival; Humans; Neoplasms; Oxidation-Reduction; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Signal Transduction
PubMed: 30706779
DOI: 10.2174/1381612825666190201120013 -
Blood Transfusion = Trasfusione Del... Jan 2022Proteasomes are proteolytic complexes with prominent roles in the control of protein homeostasis and cellular viability. However, little is known about the effects of...
BACKGROUND
Proteasomes are proteolytic complexes with prominent roles in the control of protein homeostasis and cellular viability. However, little is known about the effects of storage and glucose-6-phosphate dehydrogenase deficiency (G6PD) on the activity and topology of red blood cell (RBC) proteasomes.
MATERIALS AND METHODS
We investigated the concentration (by GeLC-MS proteomics analysis and immunoblotting), activity (by using peptide substrates and proteasome inhibitors), and subcellular/extracellular distribution (following cell fractionation and isolation of extracellular vesicles, respectively) of RBC proteasomes in fresh blood and RBCs from control and G6PD donors following storage in leukoreduced units. RBC proteasome activity was also tested in transfusion-mimicking conditions in vitro.
RESULTS
Stored RBCs were characterised by decreased cytosolic proteasome activity compared to fresh RBCs but increased membrane activity and protein concentration levels. Active proteasomes along with other "repair or destroy" proteins are recruited to the membrane during storage. A proportion of them is released in the supernatant in soluble form or inside extracellular vesicles. Significantly increased enzymatic activity and release of proteasomes were observed in G6PD vs control RBCs. Similar variations were observed in stress protein biomarkers at the G6PD membrane. The proteasome profile (mainly the caspase-like activity) had significant correlations with the G6PD metabolome and quality markers of the RBC units. The storage-induced modifications in the proteasome activities were only partly restored in transfusion-mimicking conditions.
DISCUSSION
Storage conditions and G6PD deficiency affect (individually and in synergy) the abundance, distribution, activity, and release of RBC proteasomes. The partial irreversibility of these effects in transfusion-mimicking conditions demands further investigation of their clinical impact on transfusion outcomes.
Topics: Blood Preservation; Erythrocytes; Glucosephosphate Dehydrogenase Deficiency; Humans; Oxidation-Reduction; Proteasome Endopeptidase Complex
PubMed: 33263521
DOI: 10.2450/2020.0179-20 -
Methods in Molecular Biology (Clifton,... 2018We developed a degradation assay based on fluorescent protein substrates that are efficiently recognized, unfolded, translocated, and hydrolyzed by the proteasome. The...
We developed a degradation assay based on fluorescent protein substrates that are efficiently recognized, unfolded, translocated, and hydrolyzed by the proteasome. The substrates consist of three components: a proteasome-binding tag, a folded domain, and an initiation region. All the components of the model substrate can be changed to modulate degradation, and the assay can be performed in parallel in 384-well plates. These properties allow the assay to be used to explore a wide range of experimental conditions and to screen proteasome modulators.
Topics: Biological Assay; Chromatography, Affinity; Humans; In Vitro Techniques; Kinetics; Models, Molecular; Proteasome Endopeptidase Complex; Protein Binding; Protein Conformation; Proteolysis; Substrate Specificity; Ubiquitin
PubMed: 30242719
DOI: 10.1007/978-1-4939-8706-1_21 -
Biomolecular Concepts Aug 2015Bacteria make use of compartmentalizing protease complexes, similar in architecture but not homologous to the eukaryotic proteasome, for the selective and processive... (Review)
Review
Bacteria 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.
Topics: Adenosine Triphosphatases; Bacterial Proteins; Mycobacterium tuberculosis; Proteasome Endopeptidase Complex; Protein Processing, Post-Translational; Proteolysis; Ubiquitins
PubMed: 26352358
DOI: 10.1515/bmc-2015-0017 -
Current Drug Targets 2020The ubiquitin-proteasome pathway is crucial for all cellular processes and is, therefore, a critical target for the investigation and development of novel strategies for... (Review)
Review
BACKGROUND
The ubiquitin-proteasome pathway is crucial for all cellular processes and is, therefore, a critical target for the investigation and development of novel strategies for cancer treatment. In addition, approximately 30% of newly synthesized proteins never attain their final conformations due to translational errors or defects in post-translational modifications; therefore, they are also rapidly eliminated by the ubiquitin-proteasome pathway.
OBJECTIVE
Here, an effort was made to outline the recent findings deciphering the new molecular mechanisms involved in the regulation of ubiquitin-proteasome pathway as well as the resistance mechanisms developed against proteasome inhibitors in cell culture experiments and in the clinical trials.
RESULTS
Since cancer cells have higher proliferation rates and are more prone to translational errors, they require the ubiquitin-proteasome pathway for selective advantage and sustained proliferation. Therefore, drugs targeting the ubiquitin-proteasome pathway are promising agents for the treatment of both hematological and solid cancers.
CONCLUSION
A number of proteasome inhibitors are approved and used for the treatment of advanced and relapsed multiple myeloma. Unfortunately, drug resistance mechanisms may develop very fast within days of the start of the proteasome inhibitor-treatment either due to the inherent or acquired resistance mechanisms under selective drug pressure. However, a comprehensive understanding of the mechanisms leading to the proteasome inhibitor-resistance will eventually help the design and development of novel strategies involving new drugs and/or drug combinations for the treatment of a number of cancers.
Topics: Animals; Clinical Trials as Topic; Drug Resistance, Neoplasm; Humans; Neoplasms; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Ubiquitin
PubMed: 32448101
DOI: 10.2174/1389450121666200525004714 -
Biomolecules Aug 2019The 26S proteasome is the central element of proteostasis regulation in eukaryotic cells, it is required for the degradation of protein factors in multiple cellular... (Review)
Review
The 26S proteasome is the central element of proteostasis regulation in eukaryotic cells, it is required for the degradation of protein factors in multiple cellular pathways and it plays a fundamental role in cell stability. The main aspects of proteasome mediated protein degradation have been highly (but not totally) described during three decades of intense cellular, molecular, structural and chemical biology research and tool development. Contributions accumulated within this time lapse allow researchers today to go beyond classical partial views of the pathway, and start generating almost complete views of how the proteasome acts inside the cell. These views have been recently reinforced by cryo-electron microscopy and mechanistic works that provide from landscapes of proteasomal populations distributed in distinct intracellular contexts, to detailed shots of each step of the process of degradation of a given substrate, of the factors that regulate it, and precise measurements of the speed of degradation. Here, we present an updated digest of the most recent developments that significantly contribute in our understanding of how the 26S proteasome degrades hundreds of ubiquitinated substrates in multiple intracellular environments.
Topics: Animals; Cells; Humans; Proteasome Endopeptidase Complex; Protein Transport; Proteolysis; Ubiquitination
PubMed: 31443414
DOI: 10.3390/biom9090395 -
European Journal of Medicinal Chemistry Jul 2021Proteasomes contribute to maintaining protein homeostasis and their inhibition is beneficial in certain types of cancer and in autoimmune diseases. However, the...
Proteasomes contribute to maintaining protein homeostasis and their inhibition is beneficial in certain types of cancer and in autoimmune diseases. However, the inhibition of the proteasomes in healthy cells leads to unwanted side-effects and significant effort has been made to identify inhibitors specific for the immunoproteasome, especially to treat diseases which manifest increased levels and activity of this proteasome isoform. Here, we report our efforts to discover fragment-sized inhibitors of the human immunoproteasome. The screening of an in-house library of structurally diverse fragments resulted in the identification of benzo[d]oxazole-2(3H)-thiones, benzo[d]thiazole-2(3H)-thiones, benzo[d]imidazole-2(3H)-thiones, and 1-methylbenzo[d]imidazole-2(3H)-thiones (with a general term benzoXazole-2(3H)-thiones) as inhibitors of the chymotrypsin-like (β5i) subunit of the immunoproteasome. A subsequent structure-activity relationship study provided us with an insight regarding growing vectors. Binding to the β5i subunit was shown and selectivity against the β5 subunit of the constitutive proteasome was determined. Thorough characterization of these compounds suggested that they inhibit the immunoproteasome by forming a disulfide bond with the Cys48 available specifically in the β5i active site. To obtain fragments with biologically more tractable covalent interactions, we performed a warhead scan, which yielded benzoXazole-2-carbonitriles as promising starting points for the development of selective immunoproteasome inhibitors with non-peptidic scaffolds.
Topics: Drug Evaluation, Preclinical; Humans; Inhibitory Concentration 50; Oxazoles; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Protein Subunits; Structure-Activity Relationship; Thiazoles; Thiones
PubMed: 33894528
DOI: 10.1016/j.ejmech.2021.113455