scholarly journals Nuclear polyglutamine-containing protein aggregates as active proteolytic centers

2008 ◽  
Vol 180 (4) ◽  
pp. 697-704 ◽  
Author(s):  
Min Chen ◽  
Lena Singer ◽  
Andrea Scharf ◽  
Anna von Mikecz
Keyword(s):  
Biological Function ◽  
Local Level ◽  
Sodium Dodecyl ◽  
Protein Aggregates ◽  
Ubiquitin Proteasome System ◽  
Cellular Responses ◽  
Regulatory Mechanisms ◽  
Large Protein ◽  
Ubiquitin Proteasome ◽  
Dependent Protein

Protein aggregates and nuclear inclusions (NIs) containing components of the ubiquitin–proteasome system (UPS), expanded polyglutamine (polyQ) proteins, and transcriptional coactivators characterize cellular responses to stress and are hallmarks of neurodegenerative diseases. The biological function of polyQ-containing aggregates is unknown. To analyze proteasomal activity within such aggregates, we present a nanoparticle (NP)-based method that enables controlled induction of sodium dodecyl sulfate–resistant inclusions of endogenous nuclear proteins while normal regulatory mechanisms remain in place. Consistent with the idea that the UPS maintains quality control, inhibition of proteasomal proteolysis promotes extra large protein aggregates (1.4–2 μm), whereas formation of NP-induced NIs is found to be inversely correlated to proteasome activation. We show that global proteasomal proteolysis increases in NP-treated nuclei and, on the local level, a subpopulation of NIs overlaps with focal domains of proteasome-dependent protein degradation. These results suggest that inclusions in the nucleus constitute active proteolysis modules that may serve to concentrate and decompose damaged, malfolded, or misplaced proteins.

scholarly journals The Intertwining of Autophagy and the Ubiquitin Proteasome System in Podocyte (Patho)Physiology

2021 ◽  
Vol 55 (S4) ◽  
pp. 68-95
Keyword(s):  
Protein Aggregates ◽  
Ubiquitin Proteasome System ◽  
Regulatory Mechanisms ◽  
Disease Development ◽  
Protein Homeostasis ◽  
Differential Impact ◽  
Podocyte Injury ◽  
Ubiquitin Proteasome ◽  
Lysosomal System

Protein homeostasis strongly depends on the targeted and selective removal of unneeded or flawed proteins, of protein aggregates, and of damaged or excess organelles by the two main intracellular degradative systems, namely the ubiquitin proteasomal system (UPS) and the autophagosomal lysosomal system. Despite representing completely distinct mechanisms of degradation, which underlie differing regulatory mechanisms, growing evidence suggests that the UPS and autophagy strongly interact especially in situations of overwhelming and impairment, and that both are involved in podocyte proteostasis and in the pathogenesis of podocyte injury. The differential impact of autophagy and the UPS on podocyte biology and on podocyte disease development and progression is not understood. Recent advances in understanding the role of the UPS and autophagy in podocyte biology are reviewed here.

scholarly journals Old players in new posts: the role of P53, ATM and DNAPK in DNA damage-related ubiquitylation-dependent removal of S2P RNAPII

2021 ◽  
Author(s):  
Barbara N Borsos ◽  
Vasiliki Pantazi ◽  
Zoltán G Páhi ◽  
Hajnalka Majoros ◽  
Zsuzsanna Ujfaludi ◽  
...  
Keyword(s):  
Dna Damage ◽  
Rna Polymerase Ii ◽  
E3 Ligase ◽  
Ubiquitin Proteasome System ◽  
Dna Double Strand Breaks ◽  
Damage Site ◽  
Strand Breaks ◽  
Cullin 3 ◽  
Ubiquitin Proteasome ◽  
Dependent Protein

AbstractDNA double-strand breaks are the most deleterious lesions for the cells, therefore understanding the macromolecular interactions in the DNA repair-related mechanisms is essential. DNA damage triggers transcription silencing at the damage site, leading to the removal of the elongating RNA polymerase II (S2P RNAPII) from this locus, which provides accessibility for the repair factors to the lesion. Ataxia-telangiectasia mutated (ATM) and DNA-dependent protein kinase (DNAPK) are the two main regulatory kinases of homologous recombination and non-homologous end joining, respectively. Although these kinases are involved in the activation of different repair pathways, they have common target proteins, such as P53. We previously demonstrated that following transcription block, P53 plays a pivotal role in transcription elongation process by interacting with S2P RNAPII. In the current study, we reveal that P53, ATM and DNAPK are involved in the fine-tune regulation of the ubiquitin-proteasome system-related degradation of S2P RNAPII. However, they act differently in this process: P53 delays the removal of S2P RNAPII, while ATM and DNAPK participate in the activation of members of E3 ligase complexes involved in the ubiquitylation of S2P RNAPII. We also demonstrate that WW domain-containing protein 2 (WWP2) and Cullin-3 (CUL3) are interaction partners of S2P RNAPII, thus forming a complex with the transcribing RNAPII complex.Simple SummaryTo ensure the proper repair following DNA double-strand breaks, the eviction of the arrested elongating RNA polymerase II (S2P RNAPII) is required. Here, we report an emerging role of P53, Ataxia-telangiectasia mutated (ATM) and DNA-dependent protein kinase (DNAPK) in the ubiquitin-proteasome system-dependent removal of S2P RNAPII. We also identified interactions between S2P RNAPII and WW domain-containing protein 2 (WWP2) or Cullin-3 (CUL3) (members of E3 ligase complexes), which are involved in the ubiquitylation of S2P RNAPII following DNA damage. Furthermore, the RNAPII-E3 ligase complex interactions are mediated by P53, ATM and DNAPK, which suggests potential participation of all three proteins in the effective resolution of transcription block at the damage site. Altogether, our results provide a better comprehension of the molecular background of transcription elongation block-related DNA repair processes and highlight an indispensable function of P53, ATM and DNAPK in these mechanisms.

scholarly journals Selective autophagic clearance of protein aggregates is mediated by the autophagy receptor, TAX1BP1

2019 ◽  
Author(s):  
Shireen A. Sarraf ◽  
Hetal V. Shah ◽  
Gil Kanfer ◽  
Michael E. Ward ◽  
Richard J. Youle
Keyword(s):  
Quality Control ◽  
Protein Quality ◽  
Protein Quality Control ◽  
Protein Aggregates ◽  
Ubiquitin Proteasome System ◽  
Cellular Homeostasis ◽  
Receptor Proteins ◽  
Proteotoxic Stress ◽  
Polyq Protein ◽  
Ubiquitin Proteasome

AbstractMisfolded protein aggregates can disrupt cellular homeostasis and cause toxicity, a hallmark of numerous neurodegenerative diseases. Protein quality control by the ubiquitin proteasome system (UPS) and autophagy is vital for clearance of aggregates and maintenance of cellular homeostasis1. Autophagy receptor proteins bridge the interaction between ubiquitinated proteins and the autophagy machinery allowing selective elimination of cargo2. Aggrephagy is critical to protein quality control, but how aggregates are recognized and targeted for degradation is not well understood. Here we examine the requirements for 5 autophagy receptor proteins: OPTN, NBR1, p62, NDP52, and TAX1BP1 in proteotoxic stress-induced aggregate clearance. Endogenous TAX1BP1 is both recruited to and required for the clearance of stress-induced aggregates while overexpression of TAX1BP1 increases aggregate clearance through autophagy. Furthermore, TAX1BP1 depletion sensitizes cells to proteotoxic stress and Huntington’s disease-linked polyQ proteins, whereas TAX1BP1 overexpression clears cells of polyQ protein aggregates by autophagy. We propose a broad role for TAX1BP1 in the clearance of cytotoxic proteins, thus identifying a new mode of clearance of protein inclusions.

scholarly journals The role of the ubiquitin/proteasome system in cellular responses to radiation

Oncogene ◽  
2003 ◽  
Vol 22 (37) ◽  
pp. 5755-5773 ◽  
Author(s):  
William H McBride ◽  
Keisuke S Iwamoto ◽  
Randi Syljuasen ◽  
Milena Pervan ◽  
Frank Pajonk
Keyword(s):  
Ubiquitin Proteasome System ◽  
Cellular Responses ◽  
Ubiquitin Proteasome

scholarly journals Mitochondrial ATP-Dependent Proteases—Biological Function and Potential Anti-Cancer Targets

Cancers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 2020
Author(s):  
Yue Feng ◽  
Kazem Nouri ◽  
Aaron D. Schimmer
Keyword(s):  
Mitochondrial Membrane ◽  
Biological Function ◽  
Mitochondrial Respiratory Chain ◽  
Ubiquitin Proteasome System ◽  
Mitochondrial Proteins ◽  
Protein Homeostasis ◽  
Anti Cancer ◽  
Ubiquitin Proteasome ◽  
Novel Approaches ◽  
Novel Therapeutic

Cells must eliminate excess or damaged proteins to maintain protein homeostasis. To ensure protein homeostasis in the cytoplasm, cells rely on the ubiquitin-proteasome system and autophagy. In the mitochondria, protein homeostasis is regulated by mitochondria proteases, including four core ATP-dependent proteases, m-AAA, i-AAA, LonP, and ClpXP, located in the mitochondrial membrane and matrix. This review will discuss the function of mitochondrial proteases, with a focus on ClpXP as a novel therapeutic target for the treatment of malignancy. ClpXP maintains the integrity of the mitochondrial respiratory chain and regulates metabolism by degrading damaged and misfolded mitochondrial proteins. Inhibiting ClpXP genetically or chemically impairs oxidative phosphorylation and is toxic to malignant cells with high ClpXP expression. Likewise, hyperactivating the protease leads to increased degradation of ClpXP substrates and kills cancer cells. Thus, targeting ClpXP through inhibition or hyperactivation may be novel approaches for patients with malignancy.

scholarly journals Sit4 Phosphatase Is Functionally Linked to the Ubiquitin-Proteasome System

Genetics ◽  
2003 ◽  
Vol 164 (4) ◽  
pp. 1305-1321
Author(s):  
Thorsten Singer ◽  
Stefan Haefner ◽  
Michael Hoffmann ◽  
Michael Fischer ◽  
Julia Ilyina ◽  
...  
Keyword(s):  
Minimal Medium ◽  
Synthetic Lethality ◽  
Ubiquitin Proteasome System ◽  
Yeast Cells ◽  
G1 Arrest ◽  
Cell Integrity ◽  
Synthetic Lethal ◽  
Ubiquitin Proteasome ◽  
Dependent Protein ◽  
Common Target

Abstract Using a synthetic lethality screen we found that the Sit4 phosphatase is functionally linked to the ubiquitin-proteasome system. Yeast cells harboring sit4 mutations and an impaired proteasome (due to pre1-1 pre4-1 mutations) exhibited defective growth on minimal medium. Nearly identical synthetic effects were found when sit4 mutations were combined with defects of the Rad6/Ubc2- and Cdc34/Ubc3-dependent ubiquitination pathways. Under synthetic lethal conditions, sit4 pre or sit4 ubc mutants formed strongly enlarged unbudded cells with a DNA content of 1N, indicating a defect in the maintenance of cell integrity during starvation-induced G1 arrest. Sit4-related synthetic effects could be cured by high osmotic pressure or by the addition of certain amino acids to the growth medium. These results suggest a concerted function of the Sit4 phosphatase and the ubiquitin-proteasome system in osmoregulation and in the sensing of nutrients. Further analysis showed that Sit4 is not a target of proteasome-dependent protein degradation. We could also show that Sit4 does not contribute to regulation of proteasome activity. These data suggest that both Sit4 phosphatase and the proteasome act on a common target protein.

Fas expression promotes proteasomal activity in toxin-induced parkinsonism

2012 ◽  
Vol 24 (3) ◽  
pp. 166-171
Author(s):  
Anne M. Landau ◽  
Rosmarie Siegrist-Johnstone ◽  
Julie Desbarats
Keyword(s):  
Neuroblastoma Cells ◽  
Death Receptor ◽  
Protein Aggregates ◽  
Ubiquitin Proteasome System ◽  
Wild Type ◽  
Proteasomal Activity ◽  
Ubiquitin Proteasome ◽  
Deficient Mice

Objective: Fas (CD95), commonly categorised as a death receptor due to its well-defined role in apoptosis, can paradoxically also promote neuroprotection. We have previously found that defects in Fas signalling render mice highly susceptible to neural degeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson's disease (PD). Decreased activity of the ubiquitin proteasome system and accumulation of protein aggregates are implicated in PD pathogenesis. Here, we investigate the relationship between Fas and ubiquitin proteasomal activity in neuronal cells.Methods: We performed proteasome assays in neuroblastoma cells and in midbrain cultures of wild-type and Fas-deficient mice.Results: Neuroblastoma cells upregulated proteasomal activity in response to an activating Fas antibody in vitro. Furthermore, neural tissue from Fas-deficient mice showed decreased proteasomal activity compared with the tissue from wild-type mice when exposed to a PD-inducing toxin in vivo.Conclusion: These findings suggest that mechanisms for Fas-mediated neuroprotection may include Fas-induced upregulation of proteasomal activity, and consequently less accumulation of toxic protein aggregates.

scholarly journals Tuning the proteasome to brighten the end of the journey

2016 ◽  
Vol 311 (5) ◽  
pp. C793-C804 ◽  
Author(s):  
Thibault Mayor ◽  
Michal Sharon ◽  
Michael H. Glickman
Keyword(s):  
Cell Cycle Progression ◽  
Ubiquitin Proteasome System ◽  
Proteasome Activity ◽  
Cellular Proteins ◽  
Regulatory Mechanisms ◽  
Protein Homeostasis ◽  
Cycle Progression ◽  
Cellular Processes ◽  
Age Related ◽  
Ubiquitin Proteasome

Degradation by the proteasome is the fate for a large portion of cellular proteins, and it plays a major role in maintaining protein homeostasis, as well as in regulating many cellular processes like cell cycle progression. A decrease in proteasome activity has been linked to aging and several age-related neurodegenerative pathologies and highlights the importance of the ubiquitin proteasome system regulation. While the proteasome has been traditionally viewed as a constitutive element of proteolysis, major studies have highlighted how different regulatory mechanisms can impact its activity. Importantly, alterations of proteasomal activity may have major impacts for its function and in therapeutics. On one hand, increasing proteasome activity could be beneficial to prevent the age-related downfall of protein homeostasis, whereas inhibiting or reducing its activity can prevent the proliferation of cancer cells.

scholarly journals Differential regulation of HMG-CoA reductase and Insig-1 by enzymes of the ubiquitin-proteasome system

2012 ◽  
Vol 23 (23) ◽  
pp. 4484-4494 ◽  
Author(s):  
Yien Che Tsai ◽  
Gil S. Leichner ◽  
Margaret M. P. Pearce ◽  
Gaye Lynn Wilson ◽  
Richard J. H. Wojcikiewicz ◽  
...  
Keyword(s):  
Fibroblast Cell ◽  
Ubiquitin Proteasome System ◽  
Hmg Coa Reductase ◽  
Accelerated Degradation ◽  
Rate Limiting Step ◽  
Ubiquitin Ligase E3 ◽  
Ubiquitin Proteasome ◽  
Dependent Protein ◽  
Regulatory Loop ◽  
Coa Reductase

The endoplasmic reticulum (ER)–resident enzyme 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase catalyzes the rate-limiting step in sterol production and is the therapeutic target of statins. Understanding HMG-CoA reductase regulation has tremendous implications for atherosclerosis. HMG-CoA reductase levels are regulated in response to sterols both transcriptionally, through a complex regulatory loop involving the ER Insig proteins, and posttranslationally, by Insig-dependent protein degradation by the ubiquitin-proteasome system. The ubiquitin ligase (E3) gp78 has been implicated in the sterol-regulated degradation of HMG-CoA reductase and Insig-1 through ER-associated degradation (ERAD). More recently, a second ERAD E3, TRC8, has also been reported to play a role in the sterol-accelerated degradation of HMG-CoA reductase. We interrogated this network in gp78−/− mouse embryonic fibroblasts and also assessed two fibroblast cell lines using RNA interference. Although we consistently observe involvement of gp78 in Insig-1 degradation, we find no substantive evidence to support roles for either gp78 or TRC8 in the robust sterol-accelerated degradation of HMG-CoA reductase. We discuss factors that might lead to such discrepant findings. Our results suggest a need for additional studies before definitive mechanistic conclusions are drawn that might set the stage for development of drugs to manipulate gp78 function in metabolic disorders.

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