Oxidative Stress-dependent Perturbations of 26S Proteasome Structure
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ABSTRACT: Dataset for publication submission. MS/MS and MSn analysis of in vivo cross-linked proteasomes purified from Rpn11, Rpt6, and a7-tagged 293 cell lines.
Project description:MicroRNA regulates protein expression of cells by repressing translation of specific target messenger transcripts. Loss of the neuron specific microRNA miR-128 in Dopamine D1-receptor expressing neurons in the murine striatum (D1-MSNs) lead to increased neuronal excitability, locomotor hyperactivity and fatal epilepsy. To examine expression changes in the absence of miR-128 in D1-MSNs, we used mice expressing EGFP-tagged ribosomes in D1-MSNs with either D1-MSN-specific homozygous deletion of miR-128-2 locus or no deletion. Transcripts co-immunoprecipitated with tagged ribosomes were analyzed by microarray. 9 mutant animals ( D1-MSN-tagged ribosome; D1-MSN specific miR-128-2 homozygous deletion) and 7 age matched littermate control animals (D1-MSN-tagged ribosome only).
Project description:Aging is marked by a collapse of protein homeostasis and deterioration of adaptive stress responses that often lead to disease. During aging, the induction of stress responses decline along with protein quality control. Here, we have shown that the ability to mount an adaptive response by pretreatment with minor oxidative stress is abrogated in aged Caenorhabditis elegans We have identified a defect in SKN-1 signaling sensitivity during aging and have also found an aging-related increase in basal proteasome expression and in vitro activity, however, adaptation of the 20S proteasome in response to stress is lost in old animals. Interestingly, increased activation of SKN-1 promotes stress resistance, but is unable to rescue declining adaptation during aging. Our data demonstrate that the aging-dependent decline in SKN-1 signaling negatively impacts adaptation of the 20S proteasome in response to acute oxidative stress.
Project description:Proteasomes degrade most intracellular proteins. Several different forms of proteasomes are known. Proteasome inhibitors targeting different proteasome forms are used in clinical practice and were shown to modulate long-term potentiation (LTP) in hippocampal slices of untreated animals. Here we studied the effect of chronic administration of non-constitutive proteasome inhibitor ONX-0914 on the LTP induced by two different protocols: tetanic stimulation and theta-burst stimulation (TBS). Excitatory postsynaptic potentials (fEPSPs) in hippocampal slices from control animals and animals treated with DMSO or ONX-0914 were compared. The TBS stimulation did not change LTP kinetics in hippocampal slices, however chronic administration of ONX-0914 led to the decrease in fEPSP slopes after tetanic stimulation. Observed effects correlated with differential expression of genes involved in synaptic plasticity, glutaminergic synapse and synaptic signaling. Obtained results indicate that non-constitutive proteasomes are likely involved in the tetanus-evoked LTP but not the LTP occurring after TBS, supporting the relevance and complexity of the role of proteasomes in the synaptic plasticity.
Project description:SKN-1, the Caenorhabditis elegans Nrf1/2/3 ortholog, promotes both oxidative stress resistance and longevity. SKN-1 responds to oxidative stress by upregulating genes that detoxify and defend against free radicals and other reactive molecules, a SKN-1/Nrf function that is both well-known and conserved. Here we show that SKN-1 has a broader and more complex role in maintaining cellular stress defenses. SKN-1 sustains expression and activity of the ubiquitin-proteasome system (UPS) and coordinates specific protective responses to perturbations in protein synthesis or degradation through the UPS. If translation initiation or elongation is impaired, SKN-1 upregulates overlapping sets of cytoprotective genes and increases stress resistance. When proteasome gene expression and activity are blocked, SKN-1 activates multiple classes of proteasome subunit genes in a compensatory response. SKN-1 thereby maintains UPS activity in the intestine in vivo under normal conditions and promotes survival when the proteasome is inhibited. In contrast, when translation elongation is impaired, SKN-1 does not upregulate proteasome genes, and UPS activity is then reduced. This indicates that UPS activity depends upon presence of an intact translation elongation apparatus; and it supports a model, suggested by genetic and biochemical studies in yeast, that protein synthesis and degradation may be coupled processes. SKN-1 therefore has a critical tissue-specific function in increasing proteasome gene expression and UPS activity under normal conditions, as well as when the UPS system is stressed, but mounts distinct responses when protein synthesis is perturbed. The specificity of these SKN-1-mediated stress responses, along with the apparent coordination between UPS and translation elongation activity, may promote protein homeostasis under stress or disease conditions. The data suggest that SKN-1 may increase longevity, not only through its well-documented role in boosting stress resistance, but also through contributing to protein homeostasis.
Project description:The proteasome plays a pivotal role in the cellular response to oxidative stress. Here, we used biochemical and mass spectrometric methods to investigate structural changes in the 26S proteasomes from yeast and mammalian cells exposed to hydrogen peroxide (H?O?). Oxidative stress induced the dissociation of the 20S core particle from the 19S regulatory particle of the 26S proteasome, which resulted in loss of the activities of the 26S proteasome and accumulation of ubiquitinated proteins. H?O? triggered the increased association of the proteasome-interacting protein Ecm29 with the purified 19S particle. Deletion of ECM29 in yeast cells prevented the disassembly of the 26S proteasome in response to oxidative stress, and ecm29 mutants were more sensitive to H?O? than were wild-type cells, suggesting that separation of the 19S and 20S particles is important for cellular recovery from oxidative stress. The increased amount of free 20S core particles was required to degrade oxidized proteins. The Ecm29-dependent dissociation of the proteasome was independent of Yap1, a transcription factor that is critical for the oxidative stress response in yeast, and thus functions as a parallel defense pathway against H?O?-induced stress.
Project description:This study was conducted to characterize metabolic features of the breast muscle (pectoralis major) in chickens affected with the Wooden Breast myopathy. Live birds from two purebred chicken lines and one crossbred commercial broiler population were clinically examined by manual palpation of the breast muscle (pectoralis major) at 47-48 days of age. Metabolite abundance was determined by gas chromatography/mass spectrometry (GC/MS) and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) using breast muscle tissue samples from 16 affected and 16 unaffected chickens. Muscle glycogen content was also quantified in breast muscle tissue samples from affected and unaffected chickens. In total, levels of 140 biochemicals were significantly different (FDR<0.1 and fold-change A/U>1.3 or <0.77) between affected and unaffected chickens. Glycogen content measurements were considerably lower (1.7-fold) in samples taken from Wooden Breast affected birds when compared with samples from unaffected birds. Affected tissues exhibited biomarkers related to increased oxidative stress, elevated protein levels, muscle degradation, and altered glucose utilization. Affected muscle also showed elevated levels of hypoxanthine, xanthine, and urate molecules, the generation of which can contribute to altered redox homeostasis. In conclusion, our findings show that Wooden Breast affected tissues possess a unique metabolic signature. This unique profile may identify candidate biomarkers for diagnostic utilization and provide mechanistic insight into altered biochemical processes contributing to tissue hardening associated with the Wooden Breast myopathy in commercial chickens.
Project description:Oxidative stress has been implicated in multiple human neurological and other disorders. Proteasomes are multi-subunit proteases critical for the removal of oxidatively damaged proteins. To understand stress-associated human pathologies, it is important to uncover the molecular events underlying the regulation of proteasomes upon oxidative stress. To this end, we investigated H2O2 stress-induced molecular changes of the human 26S proteasome and determined that stress-induced 26S proteasome disassembly is conserved from yeast to human. Moreover, we developed and employed a new proteomic approach, XAP (in vivo cross-linking-assisted affinity purification), coupled with stable isotope labeling with amino acids in cell culture (SILAC)-based quantitative MS, to capture and quantify several weakly bound proteasome-interacting proteins and examine their roles in stress-mediated proteasomal remodeling. Our results indicate that the adapter protein Ecm29 is the main proteasome-interacting protein responsible for stress-triggered remodeling of the 26S proteasome in human cells. Importantly, using a disuccinimidyl sulfoxide-based cross-linking MS platform, we mapped the interactions of Ecm29 within itself and with proteasome subunits and determined the architecture of the Ecm29-proteasome complex with integrative structure modeling. These results enabled us to propose a structural model in which Ecm29 intrudes on the interaction between the 20S core particle and the 19S regulatory particle in the 26S proteasome, disrupting the proteasome structure in response to oxidative stress.
Project description:Stress granules (SGs) are conserved reversible cytoplasmic condensates enriched with aggregation-prone proteins assembled in response to various stresses. Defects in disassembly have been associated with various neuro- and muscular degenerative diseases in humans. Plants appear to have efficient approaches to avoid the pathological conversion of SGs. However, how plants regulate SG dynamics is unclear. Here we show increase in either temperature or duration of heat stress reduces the molecular mobility of SG marker protein and suppresses SG clearance. Proteomics analysis and FRAP assays demonstrated 20S and 26S proteasomes as stable “core” components of SGs recruited early during the heat stress. Strikingly, while heat stress inhibits the activity of the overall proteasomes, it induces dramatic ubiquitylation of SG components and enhances the activities of SG-resident proteasomes, which degrade SG components even during the assembly phase. Their proteolytic activities enable the timely disassembly of SGs and secure the survival of plant cells during the recovery from heat stress.
Project description:Proximity labeling coupled to mass spectrometry enables in situ mapping of protein-protein interactions. Here, we have developed a strategy based on tagging of proteasomes with promiscuous biotin ligases and a newly generated mouse model to monitor the interactome of proteasomes in vivo. We demonstrate that biotin ligases can be incorporated in fully assembled proteasomes without negative impact on proteasome activity. Analysis of proteins labeled by tagged proteasomes retrieved more than half of the known proteasome-interacting proteins in a single mass spectrometry analysis, including assembly factors, activators and ubiquitin-cycle related proteins. We optimized the protocol for processing of proximity labeled samples to minimize contamination from streptavidin and implemented Data Independent Acquisition (DIA) mass spectrometry for label-free analysis. We demonstrate the utility of our workflow by identifying novel proteasome-interacting proteins, charting interactomes across mouse organs, and showing that proximity-labeling can be used to identify both endogenous and small molecule-induced proteasome substrates.
Project description:Proximity labeling coupled to mass spectrometry enables in situ mapping of protein-protein interactions. Here, we have developed a strategy based on tagging of proteasomes with promiscuous biotin ligases and a newly generated mouse model to monitor the interactome of proteasomes in vivo. We demonstrate that biotin ligases can be incorporated in fully assembled proteasomes without negative impact on proteasome activity. Analysis of proteins labeled by tagged proteasomes retrieved more than half of the known proteasome-interacting proteins in a single mass spectrometry analysis, including assembly factors, activators and ubiquitin-cycle related proteins. We optimized the protocol for processing of proximity labeled samples to minimize contamination from streptavidin and implemented Data Independent Acquisition (DIA) mass spectrometry for label-free analysis. We demonstrate the utility of our workflow by identifying novel proteasome-interacting proteins, charting interactomes across mouse organs, and showing that proximity-labeling can be used to identify both endogenous and small molecule-induced proteasome substrates.