Timer-based proteomic profiling of the ubiquitin-proteasome system reveals a substrate receptor of the GID ubiquitin ligase.
Ontology highlight
ABSTRACT:
SUBMITTER: Kong KE
PROVIDER: S-EPMC8189435 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Equine grass sickness (EGS) is an acute, predominantly fatal, multiple system neuropathy of grazing horses with reported incidence rates of ?2%. An apparently identical disease occurs in multiple species, including but not limited to cats, dogs, and rabbits. Although the precise etiology remains unclear, ultrastructural findings have suggested that the primary lesion lies in the glycoprotein biosynthetic pathway of specific neuronal populations. The goal of this study was therefore to identify the molecular processes underpinning neurodegeneration in EGS. Here, we use a bottom-up approach beginning with the application of modern proteomic tools to the analysis of cranial (superior) cervical ganglion (CCG, a consistently affected tissue) from EGS-affected patients and appropriate control cases postmortem. In what appears to be the proteomic application of modern proteomic tools to equine neuronal tissues and/or to an inherent neurodegenerative disease of large animals (not a model of human disease), we identified 2,311 proteins in CCG extracts, with 320 proteins increased and 186 decreased by greater than 20% relative to controls. Further examination of selected proteomic candidates by quantitative fluorescent Western blotting (QFWB) and subcellular expression profiling by immunohistochemistry highlighted a previously unreported dysregulation in proteins commonly associated with protein misfolding/aggregation responses seen in a myriad of human neurodegenerative conditions, including but not limited to amyloid precursor protein (APP), microtubule associated protein (Tau), and multiple components of the ubiquitin proteasome system (UPS). Differentially expressed proteins eligible for in silico pathway analysis clustered predominantly into the following biofunctions: (1) diseases and disorders, including; neurological disease and skeletal and muscular disorders and (2) molecular and cellular functions, including cellular assembly and organization, cell-to-cell signaling and interaction (including epinephrine, dopamine, and adrenergic signaling and receptor function), and small molecule biochemistry. Interestingly, while the biofunctions identified in this study may represent pathways underpinning EGS-induced neurodegeneration, this is also the first demonstration of potential molecular conservation (including previously unreported dysregulation of the UPS and APP) spanning the degenerative cascades from an apparently unrelated condition of large animals, to small animal models with altered neuronal vulnerability, and human neurological conditions. Importantly, this study highlights the feasibility and benefits of applying modern proteomic techniques to veterinary investigations of neurodegenerative processes in diseases of large animals.
| S-EPMC4638047 | biostudies-literature
Project description:Zscan4 is an early embryonic gene cluster expressed in mouse embryonic stem and induced pluripotent stem cells where it plays critical roles in genomic stability, telomere maintenance, and pluripotency. Zscan4 expression is transient, and characterized by infrequent high expression peaks that are quickly down-regulated, suggesting its expression is tightly controlled. However, little is known about the protein degradation pathway responsible for regulating the human ZSCAN4 protein levels. In this study we determine for the first time the ZSCAN4 protein half-life and degradation pathway, including key factors involved in the process, responsible for the regulation of ZSCAN4 stability. We demonstrate lysine 48 specific polyubiquitination and subsequent proteasome dependent degradation of ZSCAN4, which may explain how this key factor is efficiently cleared from the cells. Importantly, our data indicate an interaction between ZSCAN4 and the E3 ubiquitin ligase RNF20. Moreover, our results show that RNF20 depletion by gene knockdown does not affect ZSCAN4 transcription levels, but instead results in increased ZSCAN4 protein levels. Further, RNF20 depletion stabilizes the ZSCAN4 protein half-life, suggesting that RNF20 negatively regulates ZSCAN4 stability. Due to the significant cellular functions of ZSCAN4, our results have important implications in telomere regulation, stem cell biology, and cancer.
| S-EPMC5928792 | biostudies-literature
Project description:CKIP-1 is an activator of the Smurf1 ubiquitin ligase acting to promote the ubiquitylation of Smad5 and MEKK2. The mechanisms involved in the recognition and degradation of these substrates by the proteasome remain unclear. Here, we show that CKIP-1, through its leucine zipper, interacts directly with the Rpt6 ATPase of the 19S regulatory particle of the proteasome. CKIP-1 mediates the Smurf1-Rpt6 interaction and delivers the ubiquitylated substrates to the proteasome. Depletion of CKIP-1 reduces the degradation of Smurf1 and its substrates by Rpt6. These findings reveal an unexpected adaptor role of CKIP-1 in coupling the ubiquitin ligase and the proteasome.
| S-EPMC3492711 | biostudies-literature
Project description:Defining the full complement of substrates for each ubiquitin ligase remains an important challenge. Improvements in mass spectrometry instrumentation and computation and in protein biochemistry methods have resulted in several new methods for ubiquitin ligase substrate identification. Here we used the parallel adapter capture (PAC) proteomics approach to study ?TrCP2/FBXW11, a substrate adaptor for the SKP1-CUL1-F-box (SCF) E3 ubiquitin ligase complex. The processivity of the ubiquitylation reaction necessitates transient physical interactions between FBXW11 and its substrates, thus making biochemical purification of FBXW11-bound substrates difficult. Using the PAC-based approach, we inhibited the proteasome to "trap" ubiquitylated substrates on the SCF(FBXW11) E3 complex. Comparative mass spectrometry analysis of immunopurified FBXW11 protein complexes before and after proteasome inhibition revealed 21 known and 23 putatively novel substrates. In focused studies, we found that SCF(FBXW11) bound, polyubiquitylated, and destabilized RAPGEF2, a guanine nucleotide exchange factor that activates the small GTPase RAP1. High RAPGEF2 protein levels promoted cell-cell fusion and, consequently, multinucleation. Surprisingly, this occurred independently of the guanine nucleotide exchange factor (GEF) catalytic activity and of the presence of RAP1. Our data establish new functions for RAPGEF2 that may contribute to aneuploidy in cancer. More broadly, this report supports the continued use of substrate trapping proteomics to comprehensively define targets for E3 ubiquitin ligases. All proteomic data are available via ProteomeXchange with identifier PXD001062.
| S-EPMC4295375 | biostudies-literature
Project description:The AMP-activated protein kinase (AMPK) regulates cellular energy homeostasis by sensing the metabolic status of the cell. AMPK is regulated by phosphorylation and dephosphorylation as a result of changing AMP/ATP levels and by removal of inhibitory ubiquitin residues by USP10. In this context, we identified the GID-complex, an evolutionarily conserved ubiquitin-ligase-complex (E3), as a negative regulator of AMPK activity. Our data show that the GID-complex targets AMPK for ubiquitination thereby altering its activity. Cells depleted of GID-subunits mimic a state of starvation as shown by increased AMPK activity and macroautophagic/autophagic flux as well as reduced MTOR activation. Consistently, gid-genes knockdown in C. elegans results in increased organismal lifespan. This study may contribute to understand metabolic disorders such as type 2 diabetes mellitus and morbid obesity and implements alternative therapeutic approaches to alter AMPK activity.AbbreviationsACTB: actin, beta; ADP: adenosine diphosphate; AMP: adenosine monophosphate; AMPK: AMP-activated protein kinase; ARMC8: armadillo repeat containing 8; ATP: adenosine triphosphate; BafA1: bafilomycin A1; BCAA: branched chain amino acid; BICC1: BicC family RNA binding protein 1; BSA: bovine serum albumin; CAMKK2 kinase: calcium/calmodulin dependent protein kinase kinase 2, beta; CHX: cycloheximide; DMEM: Dulbecco's modified Eagle's medium; E1: ubiquitin-activating enzyme; E2: ubiquitin-conjugating enzyme; E3: ubiquitin ligase; ECAR: extracellular acidification rate; FACS: fluorescent associated cell sorter; FBP1: fructose-bisphosphatase 1; FCCP: carbonyl cyanide-4 (trifluoromethoxy) phenylhydrazone; G6P: glucose-6-phosphate; GDP: guanosine diphosphate; GFP: green fluorescent protein; GID: glucose induced degradation deficient; GMP: guanosine monophosphate; GTP: guanosine triphosphate; HBP1: high mobility group box transcription factor 1; HPRT: hypoxanthine guanine phosphoribosyl transferase; KO: knock out; LE: long exposure; MAEA: macrophage erythroblast attacher; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MKLN1: muskelin 1; mRNA: messenger RNA; MTOR: mechanistic target of rapamycin; NES: normalized enrichment score; OCR: oxygen consumption rate; PBS: phosphate buffered saline; PCK1: phosphoenolpyruvate carboxykinase 1, cytosolic; PCR: polymerase chain reaction; PFA: paraformaldehyde; RANBP9: RAN binding protein 9; RING: really interesting new gene; RMND5: required for meiotic nuclear division5 homolog; RPS6: ribosomal protein S6; RPTOR: regulatory associated protein of MTOR, complex 1; SE: short exposure; SEM: standard error of the mean; SQSTM1/p62: sequestosome 1; TSC2: tuberous sclerosis complex 2; TUBA4A: tubulin; TUBE: tandem ubiquitin binding entities; Ub: ubiquitin; UPS: ubiquitin proteasome system; WDR26: WD repeat domain 26; WT: wild type.
| S-EPMC8386601 | biostudies-literature
Project description:Ligand of Numb protein X1 (LNX1) is an E3 ubiquitin ligase that contains a catalytic RING (Really Interesting New Gene) domain and four PDZ (PSD-95, DlgA, ZO-1) domains. LNX1 can ubiquitinate Numb, as well as a number of other ligands. However, the physiological relevance of these interactions in vivo remain unclear. To gain functional insights into the LNX family, we have characterised the LNX1 interactome using affinity purification and mass spectrometry. This approach identified a large number of novel LNX1-interacting proteins, as well as confirming known interactions with NUMB and ERC2. Many of the novel interactions mapped to the LNX PDZ domains, particularly PDZ2, and many showed specificity for LNX1 over the closely related LNX2. We show that PPFIA1 (liprin-α1), KLHL11, KIF7 and ERC2 are substrates for ubiquitination by LNX1. LNX1 ubiquitination of liprin-α1 is dependent on a PDZ binding motif containing a carboxyl terminal cysteine that binds LNX1 PDZ2. Surprisingly, the neuronally-expressed LNX1p70 isoform, that lacks the RING domain, was found to promote ubiquitination of PPFIA1 and KLHL11, albeit to a lesser extent than the longer RING-containing LNX1p80 isoform. Of several E3-ligases identified in the LNX1 interactome we confirm interactions of LNX1 with MID2/TRIM1 and TRIM27. On this basis we propose a model whereby LNX1p70, despite lacking a catalytic RING domain, may function as a scaffold to promote ubiquitination of its ligands through recruitment of other E3-ligases. These findings provide functional insights into the LNX protein family, particularly the neuronal LNX1p70 isoform.
| S-EPMC5679597 | biostudies-literature
Project description:How are E3 ubiquitin ligases configured to match substrate quaternary structures? Here, by studying the yeast GID complex (mutation of which causes deficiency in glucose-induced degradation of gluconeogenic enzymes), we discover supramolecular chelate assembly as an E3 ligase strategy for targeting an oligomeric substrate. Cryoelectron microscopy (cryo-EM) structures show that, to bind the tetrameric substrate fructose-1,6-bisphosphatase (Fbp1), two minimally functional GID E3s assemble into the 20-protein Chelator-GIDSR4, which resembles an organometallic supramolecular chelate. The Chelator-GIDSR4 assembly avidly binds multiple Fbp1 degrons so that multiple Fbp1 protomers are simultaneously ubiquitylated at lysines near the allosteric and substrate binding sites. Importantly, key structural and biochemical features, including capacity for supramolecular assembly, are preserved in the human ortholog, the CTLH E3. Based on our integrative structural, biochemical, and cell biological data, we propose that higher-order E3 ligase assembly generally enables multipronged targeting, capable of simultaneously incapacitating multiple protomers and functionalities of oligomeric substrates.
| S-EPMC8189437 | biostudies-literature
Project description:Glucose-dependent regulation of carbon metabolism is a subject of intensive studies. We have previously shown that the switch from gluconeogenesis to glycolysis is associated with ubiquitin-proteasome linked elimination of the key enzyme fructose-1,6-bisphosphatase. Seven glucose induced degradation deficient (Gid)-proteins found previously in a genomic screen were shown to form a complex that binds FBPase. One of the subunits, Gid2/Rmd5, contains a degenerated RING finger domain. In an in vitro assay, heterologous expression of GST-Gid2 leads to polyubiquitination of proteins. In addition, we show that a mutation in the degenerated RING domain of Gid2/Rmd5 abolishes fructose-1,6-bisphosphatase polyubiquitination and elimination in vivo. Six Gid proteins are present in gluconeogenic cells. A seventh protein, Gid4/Vid24, occurs upon glucose addition to gluconeogenic cells and is afterwards eliminated. Forcing abnormal expression of Gid4/Vid24 in gluconeogenic cells leads to fructose-1,6-bisphosphatase degradation. This suggests that Gid4/Vid24 initiates fructose-1,6-bisphosphatase polyubiquitination by the Gid complex and its subsequent elimination by the proteasome. We also show that an additional gluconeogenic enzyme, phosphoenolpyruvate carboxykinase, is subject to Gid complex-dependent degradation. Our study uncovers a new type of ubiquitin ligase complex composed of novel subunits involved in carbohydrate metabolism and identifies Gid4/Vid24 as a major regulator of this E3.
| S-EPMC2488282 | biostudies-literature
Project description:The sarcomere protein titin is a major determinant of cardiomyocyte stiffness and ventricular distensibility. The constant mechanical stress on titin requires well-controlled protein quality control, the exact mechanisms of which have not yet been fully elucidated. Here, we analyzed E3-ligases potentially responsible for cardiac titin ubiquitination and specifically studied the involvement of the autophagosomal system in titin degradation. Pharmacological inhibition of autophagy and the proteasome in cultured primary rat cardiomyocytes significantly elevated titin ubiquitination and increased titin degradation. Using in-vitro pull down assays we identified binding of E3-ligases MuRF1-3, CHIP and Fbx32 to several titin domains. Immunofluorescence analysis showed sarcomeric localization of the E3-ligases. siRNA-mediated knock-down of the E3-ligases MuRF-1, -3 and a combination of CHIP/Fbx32 significantly reduced autophagy-related titin ubiquitination, whereas knock-down of MuRF-2 and -3 reduced proteasome-related titin ubiquitination. We demonstrated that the proteasomal and the autophagosomal-lysosomal system participate in degradation of the titin filament. We found that ubiquitination and degradation of titin are partially regulated by E3-ligases of the MuRF family. We further identified CHIP and Fbx32 as E3-ligases involved in titin ubiquitination.
| S-EPMC8548520 | biostudies-literature
Project description:Somatic mutations in the KEAP1 ubiquitin ligase or its substrate NRF2 (NFE2L2) commonly occur in human cancer, resulting in constitutive NRF2-mediated transcription of cytoprotective genes. However, many tumors display high NRF2 activity in the absence of mutation, supporting the hypothesis that alternative mechanisms of pathway activation exist. Previously, we and others discovered that via a competitive binding mechanism, the proteins WTX (AMER1), PALB2, and SQSTM1 bind KEAP1 to activate NRF2. Proteomic analysis of the KEAP1 protein interaction network revealed a significant enrichment of associated proteins containing an ETGE amino acid motif, which matches the KEAP1 interaction motif found in NRF2. Like WTX, PALB2, and SQSTM1, we found that the dipeptidyl peptidase 3 (DPP3) protein binds KEAP1 via an "ETGE" motif to displace NRF2, thus inhibiting NRF2 ubiquitination and driving NRF2-dependent transcription. Comparing the spectrum of KEAP1-interacting proteins with the genomic profile of 178 squamous cell lung carcinomas characterized by The Cancer Genome Atlas revealed amplification and mRNA overexpression of the DPP3 gene in tumors with high NRF2 activity but lacking NRF2 stabilizing mutations. We further show that tumor-derived mutations in KEAP1 are hypomorphic with respect to NRF2 inhibition and that DPP3 overexpression in the presence of these mutants further promotes NRF2 activation. Collectively, our findings further support the competition model of NRF2 activation and suggest that "ETGE"-containing proteins such as DPP3 contribute to NRF2 activity in cancer.
| S-EPMC3618590 | biostudies-literature