Dual regulation of transcription factor Nrf2 by Keap1 and by the combined actions of β-TrCP and GSK-3

2015 ◽  
Vol 43 (4) ◽  
pp. 611-620 ◽  
Author(s):  
John D. Hayes ◽  
Sudhir Chowdhry ◽  
Albena T. Dinkova-Kostova ◽  
Calum Sutherland
Keyword(s):  
Transcription Factor ◽  
Growth Factors ◽  
Ubiquitin Ligase ◽  
Molecular Mechanisms ◽  
Glycogen Synthase ◽  
Proteasomal Degradation ◽  
Regulation Of Transcription ◽  
Related Factor ◽  
Nrf2 Target Gene ◽  
The Stability

Nuclear factor-erythroid 2 p45 (NF-E2 p45)-related factor 2 (Nrf2) is a master regulator of redox homoeostasis that allows cells to adapt to oxidative stress and also promotes cell proliferation. In this review, we describe the molecular mechanisms by which oxidants/electrophilic agents and growth factors increase Nrf2 activity. In the former case, oxidants/electrophiles increase the stability of Nrf2 by antagonizing the ability of Kelch-like ECH-associated protein 1 (Keap1) to target the transcription factor for proteasomal degradation via the cullin-3 (Cul3)–RING ubiquitin ligase CRLKeap1. In the latter case, we speculate that growth factors increase the stability of Nrf2 by stimulating phosphoinositide 3-kinase (PI3K)−protein kinase B (PKB)/Akt signalling, which in turn results in inhibitory phosphorylation of glycogen synthase kinase-3 (GSK-3) and in doing so prevents the formation of a DSGIS motif-containing phosphodegron in Nrf2 that is recognized by the β-transducin repeat-containing protein (β-TrCP) Cul1-based E3 ubiquitin ligase complex SCFβ-TrCP. We present data showing that in the absence of Keap1, the electrophile tert-butyl hydroquinone (tBHQ) can stimulate Nrf2 activity and induce the Nrf2-target gene NAD(P)H:quinone oxidoreductase-1 (NQO1), whilst simultaneously causing inhibitory phosphorylation of GSK-3β at Ser9. Together, these observations suggest that tBHQ can suppress the ability of SCFβ-TrCP to target Nrf2 for proteasomal degradation by increasing PI3K−PKB/Akt signalling. We also propose a scheme that explains how other protein kinases that inhibit GSK-3 could stimulate induction of Nrf2-target genes by preventing formation of the DSGIS motif-containing phosphodegron in Nrf2.

scholarly journals Molecular and Cellular Mechanisms Associated with Effects of Molecular Hydrogen in Cardiovascular and Central Nervous Systems

Antioxidants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1281
Author(s):  
Miroslav Barancik ◽  
Branislav Kura ◽  
Tyler W. LeBaron ◽  
Roberto Bolli ◽  
Jozef Buday ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Molecular Hydrogen ◽  
Molecular Mechanisms ◽  
Glycogen Synthase ◽  
Current Knowledge ◽  
Tissue Remodeling ◽  
Related Factor ◽  
Nervous Systems ◽  
Positive Effects ◽  
Central Nervous Systems

The increased production of reactive oxygen species and oxidative stress are important factors contributing to the development of diseases of the cardiovascular and central nervous systems. Molecular hydrogen is recognized as an emerging therapeutic, and its positive effects in the treatment of pathologies have been documented in both experimental and clinical studies. The therapeutic potential of hydrogen is attributed to several major molecular mechanisms. This review focuses on the effects of hydrogen on the cardiovascular and central nervous systems, and summarizes current knowledge about its actions, including the regulation of redox and intracellular signaling, alterations in gene expressions, and modulation of cellular responses (e.g., autophagy, apoptosis, and tissue remodeling). We summarize the functions of hydrogen as a regulator of nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated redox signaling and the association of hydrogen with mitochondria as an important target of its therapeutic action. The antioxidant functions of hydrogen are closely associated with protein kinase signaling pathways, and we discuss possible roles of the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) and Wnt/β-catenin pathways, which are mediated through glycogen synthase kinase 3β and its involvement in the regulation of cellular apoptosis. Additionally, current knowledge about the role of molecular hydrogen in the modulation of autophagy and matrix metalloproteinases-mediated tissue remodeling, which are other responses to cellular stress, is summarized in this review.

scholarly journals Degradation of the Transcription Factor Gcn4 Requires the Kinase Pho85 and the SCFCDC4 Ubiquitin–Ligase Complex

2000 ◽  
Vol 11 (3) ◽  
pp. 915-927 ◽  
Author(s):  
Ariella Meimoun ◽  
Tsvi Holtzman ◽  
Ziva Weissman ◽  
Helen J. McBride ◽  
David J. Stillman ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Ubiquitin Ligase ◽  
Protein A ◽  
Purine Biosynthesis ◽  
Cell Cycle Regulators ◽  
Rich Medium ◽  
Ubiquitin Ligase Complex ◽  
Ubiquitin Conjugating Enzyme ◽  
The Stability

Gcn4, a yeast transcriptional activator that promotes the expression of amino acid and purine biosynthesis genes, is rapidly degraded in rich medium. Here we report that SCFCDC4, a recently characterized protein complex that acts in conjunction with the ubiquitin-conjugating enzyme Cdc34 to degrade cell cycle regulators, is also necessary for the degradation of the transcription factor Gcn4. Degradation of Gcn4 occurs throughout the cell cycle, whereas degradation of the known cell cycle substrates of Cdc34/SCFCDC4 is cell cycle regulated. Gcn4 ubiquitination and degradation are regulated by starvation for amino acids, whereas the degradation of the cell cycle substrates of Cdc34/SCFCDC4 is unaffected by starvation. We further show that unlike the cell cycle substrates of Cdc34/SCFCDC4, which require phosphorylation by the kinase Cdc28, Gcn4 degradation requires the kinase Pho85. We identify the critical target site of Pho85 on Gcn4; a mutation of this site stabilizes the protein. A specific Pho85-Pcl complex that is able to phosphorylate Gcn4 on that site is inactive under conditions under which Gcn4 is stable. Thus, Cdc34/SCFCDC4 activity is constitutive, and regulation of the stability of its various substrates occurs at the level of their phosphorylation.

scholarly journals Absolute Amounts and Status of the Nrf2-Keap1-Cul3 Complex within Cells

2016 ◽  
Vol 36 (24) ◽  
pp. 3100-3112 ◽  
Author(s):  
Tatsuro Iso ◽  
Takafumi Suzuki ◽  
Liam Baird ◽  
Masayuki Yamamoto
Keyword(s):  
Transcription Factor ◽  
Recombinant Protein ◽  
Ubiquitin Ligase ◽  
Stress Responses ◽  
Quantitative Information ◽  
Related Factor ◽  
Electrophilic Stress ◽  
Cullin 3 ◽  
Electrophilic Agent ◽  
Nrf2 Protein

The transcription factor Nrf2 (NF-E2-related-factor 2) is essential for the oxidative and electrophilic stress responses. Keap1 (Kelch-like-ECH-associated-protein 1), an adaptor for a cullin-3 (Cul3)-based ubiquitin ligase, regulates Nrf2 activity through proteasomal degradation, and acts as a sensor for oxidative and electrophilic stresses. The Keap1-Cul3 complex is a critical regulator of the cellular Nrf2 level, and yet quantitative information regarding their endogenous intracellular concentrations in homeostatic conditions and during stress responses is unknown. We analyzed the absolute amounts of the Nrf2, Keap1, and Cul3 proteins in five murine cell lines by comparison with serial dilutions of purified recombinant protein standards in combination with quantitative immunoblot analyses. In the basal state, the amount of Nrf2 was maintained at lower levels than those of Keap1 and Cul3 proteins, whereas the electrophilic agent diethylmaleate dramatically increased Nrf2 to a level greater than that of Keap1 and Cul3, resulting in the accumulation of Nrf2 in the nucleus. In contrast, Keap1 and Cul3 did not display any changes in their abundance, subcellular localization, or interaction in response to electrophilic stimuli. Our results demonstrate that the regulation of the Nrf2 protein level during stress responses is mediated by the activity but not the composition of the Nrf2-Keap1-Cul3 complex.

scholarly journals The molecular, cellular and pathophysiological roles of iRhom pseudoproteases

Open Biology ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 190003 ◽  
Author(s):  
Iqbal Dulloo ◽  
Sonia Muliyil ◽  
Matthew Freeman
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Molecular Mechanisms ◽  
Cellular Mechanisms ◽  
Central Function ◽  
Full Extent ◽  
Intramembrane Proteases ◽  
Growing Body ◽  
Growth Factor Signalling ◽  
The Stability

iRhom proteins are catalytically inactive relatives of rhomboid intramembrane proteases. There is a rapidly growing body of evidence that these pseudoenzymes have a central function in regulating inflammatory and growth factor signalling and consequent roles in many diseases. iRhom pseudoproteases have evolved new domains from their proteolytic ancestors, which are integral to their modular regulation and functions. Although we cannot yet conclude the full extent of their molecular and cellular mechanisms, there is a clearly emerging theme that they regulate the stability and trafficking of other membrane proteins. In the best understood case, iRhoms act as regulatory cofactors of the ADAM17 protease, controlling its function of shedding cytokines and growth factors. It seems likely that as the involvement of iRhoms in human diseases is increasingly recognized, they will become the focus of pharmaceutical interest, and here we discuss what is known about their molecular mechanisms and relevance in known pathologies.

scholarly journals The ubiquitin-conjugating enzyme UBE2E3 and its import receptor importin-11 regulate the localization and activity of the antioxidant transcription factor NRF2

2015 ◽  
Vol 26 (2) ◽  
pp. 327-338 ◽  
Author(s):  
Kendra S. Plafker ◽  
Scott M. Plafker
Keyword(s):  
Transcription Factor ◽  
Nuclear Import ◽  
Target Gene ◽  
Redox Homeostasis ◽  
Related Factor ◽  
Gene Promoters ◽  
Nrf2 Target Gene ◽  
Ubiquitin Conjugating Enzyme ◽  
Import Receptor ◽  
Conjugating Enzyme

The transcription factor NF-E2 p45–related factor (Nrf2) induces the expression of cytoprotective proteins that maintain and restore redox homeostasis. Nrf2 levels and activity are tightly regulated, and three subcellular populations of the transcription factor have been identified. During homeostasis, the majority of Nrf2 is degraded in the cytoplasm by ubiquitin (Ub)-mediated degradation. A second population is transcriptionally active in the nucleus, and a third population localizes to the outer mitochondrial membrane. Still unresolved are the mechanisms and factors that govern Nrf2 distribution between its subcellular locales. We show here that the Ub-conjugating enzyme UBE2E3 and its nuclear import receptor importin 11 (Imp-11) regulate Nrf2 distribution and activity. Knockdown of UBE2E3 reduces nuclear Nrf2, decreases Nrf2 target gene expression, and relocalizes the transcription factor to a perinuclear cluster of mitochondria. In a complementary manner, Imp-11 functions to restrict KEAP1, the major suppressor of Nrf2, from prematurely extracting the transcription factor off of a subset of target gene promoters. These findings identify a novel pathway of Nrf2 modulation during homeostasis and support a model in which UBE2E3 and Imp-11 promote Nrf2 transcriptional activity by restricting the transcription factor from partitioning to the mitochondria and limiting the repressive activity of nuclear KEAP1.

scholarly journals Unique Pattern of Component Gene Disruption in the NRF2 Inhibitor KEAP1/CUL3/RBX1 E3-Ubiquitin Ligase Complex in Serous Ovarian Cancer

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Victor D. Martinez ◽  
Emily A. Vucic ◽  
Kelsie L. Thu ◽  
Larissa A. Pikor ◽  
Roland Hubaux ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Related Factor ◽  
Ovarian Carcinomas ◽  
Nrf2 Pathway ◽  
Unique Pattern ◽  
Ubiquitin Ligase Complex ◽  
Nrf2 Target Gene ◽  
Complex Components

The NFE2-related factor 2 (NRF2) pathway is critical to initiate responses to oxidative stress; however, constitutive activation occurs in different cancer types, including serous ovarian carcinomas (OVCA). The KEAP1/CUL3/RBX1 E3-ubiquitin ligase complex is a regulator of NRF2 levels. Hence, we investigated the DNA-level mechanisms affecting these genes in OVCA. DNA copy-number loss (CNL), promoter hypermethylation, mRNA expression, and sequence mutation forKEAP1,CUL3, andRBX1were assessed in a cohort of 568 OVCA from The Cancer Genome Atlas. Almost 90% of cases exhibited loss-of-function alterations in any components of the NRF2 inhibitory complex. CNL is the most prominent mechanism of component disruption, with RBX1 being the most frequently disrupted component. These alterations were associated with reduced mRNA expression of complex components, and NRF2 target gene expression was positively enriched in 90% of samples harboring altered complex components. Disruption occurs through a unique DNA-level alteration pattern in OVCA. We conclude that a remarkably high frequency of DNA and mRNA alterations affects components of the KEAP1/CUL3/RBX1 complex, through a unique pattern of genetic mechanisms. Together, these results suggest a key role for the KEAP1/CUL3/RBX1 complex and NRF2 pathway deregulation in OVCA.

scholarly journals The E3 ubiquitin ligase Pib1 regulates effective gluconeogenic shutdown in S. cerevisiae

2019 ◽  
Author(s):  
Vineeth Vengayil ◽  
Sunil Laxman
Keyword(s):  
Ubiquitin Ligase ◽  
Glucose Repression ◽  
E3 Ubiquitin Ligase ◽  
Proteasomal Degradation ◽  
Ubiquitin E3 Ligase ◽  
Nutrient Environment ◽  
The Stability ◽  
Glucose Availability

AbstractCells use multiple mechanisms to regulate their metabolic states depending on changes in their nutrient environment. A well-known example is the response of cells to glucose availability. In S. cerevisiae cells growing in glucose-limited medium, the re-availability of glucose leads to the downregulation of gluconeogenesis, the activation of glycolysis, and robust ‘glucose repression’. However, our knowledge of the initial mechanisms mediating this glucose-dependent downregulation of the gluconeogenic transcription factors is incomplete. We used the gluconeogenic transcription factor Rds2 as a candidate with which to discover regulators of early events leading to glucose repression. Here, we identify a novel role for the E3 ubiquitin ligase Pib1 in regulating the stability and degradation of Rds2. Glucose addition to glucose-limited cells results in rapid ubiquitination of Rds2, followed by its proteasomal degradation. Through in vivo and in vitro experiments, we establish Pib1 as a ubiquitin E3 ligase that regulates Rds2 ubiquitination and stability. Notably, this Pib1 mediated Rds2 ubiquitination, followed by proteasomal degradation, is specific to the presence of glucose. Pib1 is required for complete glucose repression, and enables cells to optimally grow in competitive environments when glucose becomes re-available. Our results reveal the existence of a Pib1 E3-ubiquitin ligase mediated regulatory program that mediates glucose-repression when glucose availability is restored.

scholarly journals Regulation of Transcription Factor SP1 by the β-Catenin Destruction Complex Modulates Wnt Response

2018 ◽  
Vol 38 (22) ◽  
Author(s):  
Rafeeq Mir ◽  
Ankita Sharma ◽  
Saurabh J. Pradhan ◽  
Sanjeev Galande
Keyword(s):  
Transcription Factor ◽  
Wnt Signaling ◽  
Signaling Pathway ◽  
Target Genes ◽  
Glycogen Synthase ◽  
Wnt Signaling Pathway ◽  
Feedback Mechanism ◽  
Regulation Of Transcription ◽  
Dependent Manner ◽  
Factor Specificity

ABSTRACT The ubiquitous transcription factor specificity protein 1 (SP1) is heavily modified posttranslationally. These modifications are critical for switching its functions and modulation of its transcriptional activity and DNA binding and stability. However, the mechanism governing the stability of SP1 by cellular signaling pathways is not well understood. Here, we provide biochemical and functional evidence that SP1 is an integral part of the Wnt signaling pathway. We identified a phosphodegron motif in SP1 that is specific to mammals. In the absence of Wnt signaling, glycogen synthase kinase 3β (GSK3β)-mediated phosphorylation and β-TrCP E3 ubiquitin ligase-mediated ubiquitination are required to induce SP1 degradation. When Wnt signaling is on, SP1 is stabilized in a β-catenin-dependent manner. SP1 directly interacts with β-catenin, and Wnt signaling induces the stabilization of SP1 by impeding its interaction with β-TrCP and axin1, components of the destruction complex. Wnt signaling suppresses ubiquitination and subsequent proteosomal degradation of SP1. Furthermore, SP1 regulates Wnt-dependent stability of β-catenin and their mutual stabilization is critical for target gene expression, suggesting a feedback mechanism. Upon stabilization, SP1 and β-catenin cooccupy the promoters of TCFL2/β-catenin target genes. Collectively, this study uncovers a direct link between SP1 and β-catenin in the Wnt signaling pathway.

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