scholarly journals USP7 inhibits Wnt/β-catenin signaling through promoting stabilization of Axin

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Lei Ji ◽  
Bo Lu ◽  
Raffaella Zamponi ◽  
Olga Charlat ◽  
Robert Aversa ◽  
...  
Keyword(s):  
Osteoblast Differentiation ◽  
Adipocyte Differentiation ◽  
Ubiquitin Proteasome System ◽  
Cellular Systems ◽  
Negative Regulator ◽  
Scaffolding Protein ◽  
Complex Stability ◽  
Genetic Ablation ◽  
Ubiquitin Proteasome ◽  
Potent Negative Regulator

Abstract Axin is a key scaffolding protein responsible for the formation of the β-catenin destruction complex. Stability of Axin protein is regulated by the ubiquitin-proteasome system, and modulation of cellular concentration of Axin protein has a profound effect on Wnt/β-catenin signaling. Although E3s promoting Axin ubiquitination have been identified, the deubiquitinase responsible for Axin deubiquitination and stabilization remains unknown. Here, we identify USP7 as a potent negative regulator of Wnt/β-catenin signaling through CRISPR screens. Genetic ablation or pharmacological inhibition of USP7 robustly increases Wnt/β-catenin signaling in multiple cellular systems. USP7 directly interacts with Axin through its TRAF domain, and promotes deubiquitination and stabilization of Axin. Inhibition of USP7 regulates osteoblast differentiation and adipocyte differentiation through increasing Wnt/β-catenin signaling. Our study reveals a critical mechanism that prevents excessive degradation of Axin and identifies USP7 as a target for sensitizing cells to Wnt/β-catenin signaling.

scholarly journals Innate immunity to yeast prions: Btn2p and Cur1p curing of the [URE3] prion is prevented by 60S ribosomal protein deficiency or ubiquitin/proteasome system overactivity

Genetics ◽  
2021 ◽  
Author(s):  
Evgeny E Bezsonov ◽  
Herman K Edskes ◽  
Reed B Wickner
Keyword(s):  
Ubiquitin Ligase ◽  
Ribosomal Subunit ◽  
Ubiquitin Proteasome System ◽  
Negative Regulator ◽  
Large Ribosomal Subunit ◽  
Seed Number ◽  
Wild Type ◽  
Yeast Prions ◽  
In The Wild ◽  
Ubiquitin Proteasome

Abstract [URE3] is an amyloid-based prion of Ure2p, a negative regulator of poor nitrogen source catabolism in Saccharomyces cerevisiae. Overproduced Btn2p or its paralog Cur1p, in processes requiring Hsp42, cure the [URE3] prion. Btn2p cures by collecting Ure2p amyloid filaments at one place in the cell. We find that rpl4aΔ, rpl21aΔ, rpl21bΔ, rpl11bΔ and rpl16bΔ (large ribosomal subunit proteins) or ubr2Δ (ubiquitin ligase targeting Rpn4p, an activator of proteasome genes) reduce curing by overproduced Btn2p or Cur1p. Impaired curing in ubr2Δ or rpl21bΔ is restored by an rpn4Δ mutation. No effect of rps14aΔ or rps30bΔ on curing was observed, indicating that 60S subunit deficiency specifically impairs curing. Levels of Hsp42p, Sis1p or Btn3p are unchanged in rpl4aΔ, rpl21bΔ or ubr2Δ mutants. Overproduction of Cur1p or Btn2p was enhanced in rpn4Δ and hsp42Δ mutants, lower in ubr2Δ strains, and restored to above wild type levels in rpn4Δ ubr2Δ strains. As in the wild-type, Ure2N-GFP colocalizes with Btn2-RFP in rpl4aΔ, rpl21bΔ or ubr2Δ strains, but not in hsp42Δ. Btn2p/Cur1p overproduction cures [URE3] variants with low seed number, but seed number is not increased in rpl4aΔ, rpl21bΔ or ubr2Δ mutants. Knockouts of genes required for the protein sorting function of Btn2p did not affect curing of [URE3], nor did inactivation of the Hsp104 prion-curing activity. Overactivity of the ubiquitin/proteasome system, resulting from 60S subunit deficiency or ubr2Δ, may impair Cur1p and Btn2p curing of [URE3] by degrading Cur1p, Btn2p or another component of these curing systems.

scholarly journals E3 Ubiquitin Ligase-Mediated Regulation of Osteoblast Differentiation and Bone Formation

2021 ◽  
Vol 9 ◽  
Author(s):  
Jianlin Shen ◽  
Bowen Fu ◽  
Yanfang Li ◽  
Yanjiao Wu ◽  
Hongxun Sang ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Bone Formation ◽  
Osteoblast Differentiation ◽  
Deep Understanding ◽  
Ubiquitin Proteasome System ◽  
E3 Ligases ◽  
Ubiquitin Proteasome ◽  
Ubiquitin Moiety ◽  
Regulatory Effects ◽  
And Function

The ubiquitin–proteasome system (UPS) is an essential pathway that regulates the homeostasis and function of intracellular proteins and is a crucial protein-degradation system in osteoblast differentiation and bone formation. Abnormal regulation of ubiquitination leads to osteoblast differentiation disorders, interfering with bone formation and ultimately leading to osteoporosis. E3 ubiquitin ligases (E3) promote addition of a ubiquitin moiety to substrate proteins, specifically recognizing the substrate and modulating tyrosine kinase receptors, signaling proteins, and transcription factors involved in the regulation of osteoblast proliferation, differentiation, survival, and bone formation. In this review, we summarize current progress in the understanding of the function and regulatory effects of E3 ligases on the transcription factors and signaling pathways that regulate osteoblast differentiation and bone formation. A deep understanding of E3 ligase-mediated regulation of osteoblast differentiation provides a scientific rationale for the discovery and development of novel E3-targeting therapeutic strategies for osteoporosis.

scholarly journals IMiDs induce FAM83F degradation via an interaction with CK1α to attenuate Wnt signalling

2020 ◽  
Author(s):  
Karen Dunbar ◽  
Thomas J. Macartney ◽  
Gopal P. Sapkota
Keyword(s):  
Plasma Membrane ◽  
Protein Complexes ◽  
Ubiquitin Proteasome System ◽  
Specific Protein ◽  
Protective Role ◽  
Wnt Signalling ◽  
Target Protein ◽  
Genetic Ablation ◽  
Ubiquitin Proteasome ◽  
Canonical Wnt

ABSTRACTImmunomodulatory imide drugs (IMiDs) bind CRBN, a substrate receptor of the Cul4A E3 ligase complex, enabling neo-substrate recruitment and degradation via the ubiquitin-proteasome system. Here, we report FAM83F as such a neo-substrate. We recently showed that the eight FAM83 proteins (A-H) interact with members of the serine/threonine protein kinase CK1 family, to regulate their subcellular distribution and distinct biological roles. CK1α is a well-established IMiD neo-substrate and we demonstrate here that IMiD-induced FAM83F degradation requires its association with CK1α. Despite all FAM83 proteins interacting with CK1α, no other FAM83 protein is degraded by IMiDs. FAM83F is localised to the plasma membrane, and consistent with this, IMiD treatment results in depletion of both FAM83F and CK1α levels from the plasma membrane. We have recently identified FAM83F as a mediator of the canonical Wnt signalling pathway. The IMiD-induced degradation of FAM83F attenuated Wnt signalling in colorectal cancer cells and removed CK1α from the plasma membrane, mirroring the phenotypes observed with genetic ablation of FAM83F. Intriguingly, in many cancer cell lines, IMiD-induced degradation of CK1α is only modest and incomplete. In line with this observation, the expression of FAM83G, which also binds to CK1α, appears to attenuate the IMiD-induced degradation of CK1α, suggesting a protective role for FAM83G on CK1α. Our findings reveal that the efficiency of target protein degradation by IMiDs, and perhaps other degraders such as PROTACs, relies on the nature of the inherent multiprotein complex in which the target protein exists. Our findings unearth opportunities for developing degraders to target specific protein complexes.

scholarly journals Nek2 Stabilization By Usp7 Leads to Activation of NF-Kb in Multiple Myeloma

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 4418-4418 ◽  
Author(s):  
Reinaldo Franqui Machin ◽  
Xin Zhan ◽  
Hongwei Xu ◽  
Ivana Frech ◽  
Guido J Tricot ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Lines ◽  
Conflicts Of Interest ◽  
Affinity Purification ◽  
Ubiquitin Proteasome System ◽  
Negative Regulator ◽  
Luciferase Assay ◽  
Luciferase Reporter ◽  
Ubiquitin Proteasome ◽  
Affinity Purification Mass Spectrometry

Abstract NIMA (Never In Mitosis Gene A)-Related Kinase 2 (Nek2), a centrosomal Serine/Threonine kinase, is a key player in numerous malignancies. Overexpression of Nek2 has been related to many cancers including Multiple Myeloma (MM). In MM, Nek2 is one of the chromosomal instability genes associated with drug resistance and disease relapse. However, very little is known about the mechanisms that lead to these Nek2-driven disparities. Here, we show that the Ubiquitin Specific Peptidase 7 (USP7) stabilizes Nek2 leading to activation of NF-kb pathway. Using gene expression profile (GEP) data from patients and cell lines we discovered that Nek2 overexpression leads to increases of several targets of the NF-kb pathway. We, thus, hypothesize that Nek2 is activating NF-kb. To address this, we overexpressed Nek2 and tested the classic canonical NF-kb hallmarks proteins by western blotting. Nek2 overexpression led to an increase in phosphorylation of IKK, activator of NF-kb, and to decrease levels of IKb-alpha, a negative regulator of the pathway. Nek2 overexpression also increased nuclear and phosphorylated p65 on residue S536, known as active transcriptional site. To further confirm that Nek2 is activating canonical NF-kb luciferase assay was performed. The luciferase reporter is driven by a p65 promoter and in cells overexpressing Nek2 luciferase levels were increased. To characterize Nek2 interacting partners a tandem affinity purification/mass spectrometry (TAP/MS) approach was performed. We found that Nek2 binds to Usp7, a deubiquitinase overexpressed in numerous cancers. This led to hypothesize that that Nek2, a known target of the ubiquitin proteasome system, is being stabilized by the Usp7 contributing to its overexpression and the increased activation of the NF-kb pathway. To test our hypothesis, we treated different cancer cell lines with the commercially available Usp7 inhibitor, P5091, or silenced the protein using shRNA. In both case, we found a reduction in Nek2 protein level. Additionally, we overexpressed Usp7 and Nek2 increased confirming that Usp7 stabilizes Nek2. To further show that Usp7 stabilizes Nek2 by de-ubiquitination, we overexpressed Usp7 and analyzed Nek2 ubiquitination after immunoprecipitation. When Usp7 was overexpressed no ubiquitination of Nek2 was detected. Finally, by using GEP data from MM patients, we found that individuals who overexpressed Nek2 along with an active NF-kb signature have worst event free survival as well as overall survival, indicating Nek2 overexpression leading to increased NF-kb signature has clinical significance. Disclosures No relevant conflicts of interest to declare.

scholarly journals Negative Regulator of Ubiquitin-Like Protein 1 modulates the autophagy–lysosomal pathway via p62 to facilitate the extracellular release of tau following proteasome impairment

2019 ◽  
Vol 29 (1) ◽  
pp. 80-96 ◽  
Author(s):  
Rosellina Guarascio ◽  
Dervis Salih ◽  
Marina Yasvoina ◽  
Frances A Edwards ◽  
Michael E Cheetham ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Proteasome Inhibition ◽  
Ubiquitin Proteasome System ◽  
Proteasomal Degradation ◽  
Tau Phosphorylation ◽  
Negative Regulator ◽  
Autophagy Flux ◽  
Extracellular Release ◽  
Uba Domain ◽  
Ubiquitin Proteasome

Abstract Negative regulator of ubiquitin-like protein 1 (NUB1) and its longer isoform NUB1L are ubiquitin-like (UBL)/ubiquitin-associated (UBA) proteins that facilitate the targeting of proteasomal substrates, including tau, synphilin-1 and huntingtin. Previous data revealed that NUB1 also mediated a reduction in tau phosphorylation and aggregation following proteasome inhibition, suggesting a switch in NUB1 function from targeted proteasomal degradation to a role in autophagy. Here, we delineate the mechanisms of this switch and show that NUB1 interacted specifically with p62 and induced an increase in p62 levels in a manner facilitated by inhibition of the proteasome. NUB1 moreover increased autophagosomes and the recruitment of lysosomes to aggresomes following proteasome inhibition. Autophagy flux assays revealed that NUB1 affected the autophagy–lysosomal pathway primarily via the UBA domain. NUB1 localized to cytosolic inclusions with pathological forms of tau, as well as LAMP1 and p62 in the hippocampal neurons of tauopathy mice. Finally, NUB1 facilitated the extracellular release of tau following proteasome inhibition. This study thus shows that NUB1 plays a role in regulating the autophagy–lysosomal pathway when the ubiquitin proteasome system is compromised, thus contributing to the mechanisms targeting the removal of aggregation-prone proteins upon proteasomal impairment.

scholarly journals Role of Ubiquitin-proteasome system in Espematogenesis

2018 ◽  
Vol 2 (4) ◽  
pp. 621-634
Author(s):  
Héctor Zapata ◽  
Patricio Morales ◽  
Marco Jara
Keyword(s):  
Gene Expression ◽  
Ubiquitin Proteasome System ◽  
Round Spermatid ◽  
Cellular Systems ◽  
Cellular Proteins ◽  
Covalent Attachment ◽  
Multienzyme Complex ◽  
Cytosolic Proteins ◽  
Ubiquitin Proteasome

Spermatogenesis is a series of events that constitute programmed cell differentiation, with dramatic changes in morphology, biochemistry and gene expression which are regulated by temporal and especially endocrine, paracrine and autocrine mechanisms. During the various stages of spermatogenesis and particularly during the differentiation of spermatids, there is massive degradation of cytosolic proteins, nuclear and membrane due to the elimination of much of the cytoplasm which has round spermatid. This protein degradation occurs within the seminiferous epithelium and is mediated by cellular systems described for this purpose. The proteasome is a multienzyme complex responsible for degrading the majority of nuclear and cytosolic proteins, after they are marked for destruction by covalent attachment of ubiquitin molecules. This selective destruction of cellular proteins is a key mechanism in the process of spermatogenesis. This article discusses the basics of male gonadal physiological process and the current understanding of the role of the ubiquitin proteasome system in the functional maintenance of spermatogenesis are reviewed.

scholarly journals Multilayered regulation of proteome stoichiometry

2021 ◽  
Author(s):  
Koji Ishikawa
Keyword(s):  
Dosage Compensation ◽  
Protein Level ◽  
Gene Dosage ◽  
Gene Copy Number ◽  
Ubiquitin Proteasome System ◽  
Cellular Systems ◽  
Gene Copy ◽  
Selective Degradation ◽  
Genetic Perturbations ◽  
Ubiquitin Proteasome

AbstractCellular systems depend on multiprotein complexes whose functionalities require defined stoichiometries of subunit proteins. Proper stoichiometry is achieved by controlling the amount of protein synthesis and degradation even in the presence of genetic perturbations caused by changes in gene dosage. As a consequence of increased gene copy number, excess subunits unassembled into the complex are synthesized and rapidly degraded by the ubiquitin–proteasome system. This mechanism, called protein-level dosage compensation, is widely observed not only under such perturbed conditions but also in unperturbed physiological cells. Recent studies have shown that recognition of unassembled subunits and their selective degradation are intricately regulated. This review summarizes the nature, strategies, and increasing complexity of protein-level dosage compensation and discusses possible mechanisms for controlling proteome stoichiometry in multiple layers of biological processes.

The ubiquitin–proteasome system and skeletal muscle wasting

2005 ◽  
Vol 41 ◽  
pp. 173-186 ◽  
Author(s):  
Didier Attaix ◽  
Sophie Ventadour ◽  
Audrey Codran ◽  
Daniel Béchet ◽  
Daniel Taillandier ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Wasting ◽  
Proteolytic Enzymes ◽  
Cathepsin L ◽  
Ubiquitin Proteasome System ◽  
Complete Breakdown ◽  
Skeletal Muscle Proteins ◽  
Ubiquitin Proteasome ◽  
Tripeptidyl Peptidase Ii ◽  
F Box Protein

The ubiquitin–proteasome system (UPS) is believed to degrade the major contractile skeletal muscle proteins and plays a major role in muscle wasting. Different and multiple events in the ubiquitination, deubiquitination and proteolytic machineries are responsible for the activation of the system and subsequent muscle wasting. However, other proteolytic enzymes act upstream (possibly m-calpain, cathepsin L, and/or caspase 3) and downstream (tripeptidyl-peptidase II and aminopeptidases) of the UPS, for the complete breakdown of the myofibrillar proteins into free amino acids. Recent studies have identified a few critical proteins that seem necessary for muscle wasting {i.e. the MAFbx (muscle atrophy F-box protein, also called atrogin-1) and MuRF-1 [muscle-specific RING (really interesting new gene) finger 1] ubiquitin–protein ligases}. The characterization of their signalling pathways is leading to new pharmacological approaches that can be useful to block or partially prevent muscle wasting in human patients.

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