Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P62988 (Ubiquitin)
 4,326 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

P62 is capable of binding the polyubiquitin chain that targets proteins for degradation by the proteasome through its ubiquitin associated domain (UBA). Immunostaining of hepatocytes from human liver with alcoholic hepatitis showed colocalization of ubiquitin and P62 in Mallory bodies. Rats fed ethanol chronically and their controls showed that P62 is colocalized with the proteasome in hepatocytes as shown by confocal microscopy. P62 cosedimented with 26S proteasomes isolated from livers of control and alcohol fed rats. P62 was increased in the 26S proteasome fraction when the proteasome chymotrypsin-like (ChT-L) activity decreased in rats fed ethanol. PS-341, a potent proteasome inhibitor was used to compare the inhibition of the proteasome with the inhibition which occurs with ethanol feeding. P62 protein levels were also increased in the purified proteasome fraction of rats given PS-341. This data indicates that modifications in P62 occur due to proteasome inhibition in experimental alcoholic liver disease.
Life Sci 2005 Sep 30
PMID:Modifications in P62 occur due to proteasome inhibition in alcoholic liver disease. 1596 33

Activation of the transcription factor Nrf2 regulates expression of phase II enzymes and other adaptive responses to electrophile and oxidant stress. Nrf2 concentrations are regulated by the thiol-rich sensor protein Keap1, which is an adaptor protein for Cul3-dependent ubiquitination and degradation of Nrf2. However, the links between site specificity of Keap1 modification by electrophiles and mechanisms of Nrf2 activation are poorly understood. We studied the actions of the prototypical Nrf2 inducer tert-butylhydroquinone (tBHQ) and two biotin-tagged, thiol-reactive electrophiles, N-iodoacetyl-N-biotinylhexylenediamine (IAB) and 1-biotinamido-4-(4'-[maleimidoethyl-cyclohexane]-carboxamido)butane (BMCC). Both IAB and tBHQ induced antioxidant response element (ARE)-directed green fluorescent protein (GFP) expression in ARE/thymidine kinase GFP HepG2 cells, and both initiated nuclear Nrf2 accumulation and induction of heme oxygenase 1 in HEK293 cells. In contrast, BMCC produced none of these effects. Liquid chromatography tandem mass spectrometry (MS-MS) analysis of human Keap1 modified by IAB or BMCC in vitro indicated that IAB adduction occurred primarily in the central linker domain, whereas BMCC modified other Keap1 domains. Treatment of FLAG-Keap1-transfected HEK293 with the Nrf2-activating compounds IAB and tBHQ generated high molecular weight Keap1 forms, which were identified as K-48-linked polyubiquitin conjugates by immunoblotting and liquid chromatography MS-MS. Keap1 polyubiquitination coincided with Nrf2 stabilization and nuclear accumulation. In contrast, BMCC did not induce Keap1 polyubiquitination. Our results suggest that Nrf2 activation is regulated through the polyubiquitination of Keap1, which in turn is triggered by specific patterns of electrophile modification of the Keap1 central linker domain. These results suggest that Keap1 adduction triggers a switching of Cul3-dependent ubiquitination from Nrf2 to Keap1, leading to Nrf2 activation.
J Biol Chem 2005 Sep 09
PMID:Specific patterns of electrophile adduction trigger Keap1 ubiquitination and Nrf2 activation. 1598 29

Semantic dementia is a syndrome of progressive deterioration in semantic memory (knowledge of objects, people, concepts and words). It falls within the clinical spectrum of frontotemporal dementia but its pathology is yet to be studied systematically. This study included 18 consecutive post mortem cases meeting clinical criteria for semantic dementia. Clinic records and diagnostic histopathology were available for all cases; structural neuroimaging, neuropsychology and semi-quantitative histopathology/immunohistochemistry data were analysed where possible. The pathological diagnosis in a clear majority of cases was frontotemporal degeneration with ubiquitin inclusions (n = 13). Eleven of these cases had characteristic motor neuron disease-type inclusions in the dentate gyrus and cerebral cortex. Ubiquitin inclusions were found only in the inferior olivary nucleus in the other two, one of which was the only case to show degeneration of motor tracts and also to have shown evidence of motor neuron disease during life. None of the patients had motor symptoms or signs at presentation. A family history of motor neuron disease was documented in one case. Pick body-positive Pick's disease appeared three times. Two cases had Alzheimer's disease and significant coincidental Alzheimer-type pathology was also found in one of the ubiquitin inclusion cases. One of the Alzheimer's disease patients had changes in white matter signal on scanning, whereas all other scans showed cerebral atrophy only. Semi-quantitative assessment of regional neuronal loss found that anterior and inferior temporal regions bore the brunt of disease across all histopathological subtypes, usually on the left side, implicating this region in semantic processing.
Brain 2005 Sep
PMID:The pathological basis of semantic dementia. 1612 79

Degradation of misfolded and damaged proteins by the 26 S proteasome requires the substrate to be tagged with a polyubiquitin chain. Assembly of polyubiquitin chains and subsequent substrate labeling potentially involves three enzymes, an E1, E2, and E3. E2 proteins are key enzymes and form a thioester intermediate through their catalytic cysteine with the C-terminal glycine (Gly76) of ubiquitin. This thioester intermediate is easily hydrolyzed in vitro and has eluded structural characterization. To overcome this, we have engineered a novel ubiquitin-E2 disulfide-linked complex by mutating Gly76 to Cys76 in ubiquitin. Reaction of Ubc1, an E2 from Saccharomyces cerevisiae, with this mutant ubiquitin resulted in an ubiquitin-E2 disulfide that could be purified and was stable for several weeks. Chemical shift perturbation analysis of the disulfide ubiquitin-Ubc1 complex by NMR spectroscopy reveals an ubiquitin-Ubc1 interface similar to that for the ubiquitin-E2 thioester. In addition to the typical E2 catalytic domain, Ubc1 contains an ubiquitin-associated (UBA) domain, and we have utilized NMR spectroscopy to demonstrate that in this disulfide complex the UBA domain is freely accessible to non-covalently bind a second molecule of ubiquitin. The ability of the Ubc1 to bind two ubiquitin molecules suggests that the UBA domain does not interact with the thioester-bound ubiquitin during polyubiquitin chain formation. Thus, construction of this novel ubiquitin-E2 disulfide provides a method to characterize structurally the first step in polyubiquitin chain assembly by Ubc1 and its related class II enzymes.
J Biol Chem 2005 Sep 09
PMID:Ubiquitin manipulation by an E2 conjugating enzyme using a novel covalent intermediate. 1601 32

Spinocerebellar ataxia type 3 is a human neurodegenerative disease resulting from polyglutamine tract expansion. The affected protein, ataxin-3, which contains an N-terminal Josephin domain followed by tandem ubiquitin (Ub)-interacting motifs (UIMs) and a polyglutamine stretch, has been implicated in the function of the Ub proteasome system. NMR-based structural analysis has now revealed that the Josephin domain binds Ub and has a papain-like fold that is reminiscent of that of other deubiquitinases, despite primary sequence divergence but consistent with its deubiqutinating activity. Mutation of the catalytic Cys enhances the stability of a complex between ataxin-3 and polyubiquitinated proteins. This effect depends on the integrity of the UIM region, suggesting that the UIMs are bound to the substrate polyubiquitin during catalysis. We propose that ataxin-3 functions as a polyubiquitin chain-editing enzyme.
Proc Natl Acad Sci U S A 2005 Sep 06
PMID:Deubiquitinating function of ataxin-3: insights from the solution structure of the Josephin domain. 1611 78

The polyubiquitin-binding protein p62 has been shown to localize in aggregates common to several types of diseases. Here, we report that p62 forms independent fibrillar aggregates in vitro in a time- and concentration-dependent manner. FTIR spectra and ThT fluorescence assay of p62 reveals increased beta-sheet content as aggregates form compared to the native protein. The fibrillar nature of the aggregates was observed by transmission electron microscopy. Overexpression of p62 in HEK cells results in aggregate formation that may protect cells from apoptosis. Altogether, these results suggest that p62 fibrils may influence cell viability and indicates an important role for p62 in aggresome formation.
FEBS Lett 2005 Sep 12
PMID:Evidence for p62 aggregate formation: role in cell survival. 1612 34

The ubiquitin-pathway associated (UBA) domain is a 40-residue polyubiquitin-binding motif. The Schizosaccharomyces pombe protein Mud1 is an ortholog of the Saccharomyces cerevisiae DNA-damage response protein Ddi1 and binds to K48-linked polyubiquitin through its UBA domain. We have solved the crystal structure of Mud1 UBA at 1.8 angstroms resolution, revealing a canonical three-helical UBA fold. We have probed the interactions of this domain using mutagenesis, surface plasmon resonance, NMR and analytical ultracentrifugation. We show that the ubiquitin-binding surface of Mud1 UBA extends beyond previously recognized motifs and can be functionally dissected into primary and secondary ubiquitin-binding sites. Mutation of Phe330 to alanine, a residue exposed between helices 2 and 3, significantly reduces the affinity of the Mud1 UBA domain for K48-linked polyubiquitin, despite leaving the primary binding surface functionally intact. Moreover, K48-linked diubiquitin binds a single Mud1 UBA domain even in the presence of excess UBA. We therefore propose a mechanism for the recognition of K48-linked polyubiquitin chains by Mud1 in which diubiquitin units are specifically recognized by a single UBA domain.
EMBO J 2005 Sep 21
PMID:Mechanism of Lys48-linked polyubiquitin chain recognition by the Mud1 UBA domain. 1613 82

We have developed an ultrafast pulse method for protein surface footprinting by laser-induced protein surface oxidations. This method makes use of a pulse UV laser that produces, in nanoseconds, a high concentration of hydroxyl (OH) free radicals by photodissociation of a hydrogen peroxide (H2O2) solution. The OH radicals oxidize amino acid residues located on the protein surface to produce stable covalent modifications. The oxidized protein is then analyzed by mass spectrometry to map the oxidized amino acid residues. Ubiquitin and apomyoglobin were used as model proteins in this study. Our results show that a single laser pulse can produce extensive protein surface oxidations. We found that monooxidized ubiquitins were more susceptible to further oxidations by subsequent laser irradiation, as compared to nonoxidized ones. This is due to the conformational changes of proteins by oxidation that increases the solvent-accessible surface area. Therefore, it is crucial to perform this experiment with a single pulse of laser so as to avoid oxidation of proteins after conformation of the protein changes. Subsequently, to obtain a high frequency and coverage of the oxidation sites while keeping the number of laser shots to one, we further optimized the laser power and concentration of hydrogen peroxide as well as the concentration of protein. This ultrafast OH radical generation method allows for rapid and accurate detection of surface residues, enabling mapping of the solvent-accessible regions of a protein in its native state.
Anal Chem 2005 Sep 15
PMID:Nanosecond laser-induced photochemical oxidation method for protein surface mapping with mass spectrometry. 1624 30

We recently cloned the full-length cDNA of a tumour-associated protein. The recombinant protein expressed in bacteria and referred to as angiocidin has potent antitumour activity in vivo and in vitro. Angiocidin inhibits tumour growth and angiogenesis by inducing apoptosis in endothelial cells. Based on the sequence similarity of angiocidin to S5a, one of the major polyubiquitin recognition proteins in eukaryotic cells, we postulated that the antiendothelial activity of angiocidin could be due in part to its polyubiquitin binding activity. In support of this hypothesis, we show that angiocidin binds polyubiquitin in vivo with high affinity and colocalises with ubiquitinated proteins on the surface of endothelial cells. Binding is blocked with an antiubiquitin antibody. Angiocidin treatment of endothelial cells transfected with a proteasome fluorescent reporter protein showed a dose-dependent inhibition of proteasome activity and accumulation of polyubiquitinated proteins. Full-length angiocidin bound polyubiquitin while three angiocidin recombinant proteins whose putative polyubiquitin binding sites were mutated either failed to bind polyubiquitin or had significantly diminished binding activity. The in vitro apoptotic activity of these mutants correlated with their polyubiquitin binding activity. These data strongly argue that the apoptotic activity of angiocidin is dependent on its polyubiquitin binding activity.
Br J Cancer 2005 Sep 19
PMID:Endothelial apoptotic activity of angiocidin is dependent on its polyubiquitin binding activity. 1622 12

In order to clarify the onset mechanisms of drug-induced allergies, three fluorescent-labelled compounds were synthesized by subjecting sulfanilamide (SA), a base compound for sulfonamides, and its active metabolites, i.e. sulfanilamide hydroxylamine and sulfanilamide nitroso, to dansylation using dansylchloride. In other words, 5-dimethylamino-N-(4-aminobenzyl)-naphthalenesulfonamide (DNS-4ABA), 5-dimethylamino-N-(4-hydroxylaminobenzyl)-1-naphthalenesulfonamide (DNS-4HABA) and 5-dimethylamino-N-(4-nitrosobenzyl)-1-naphthalenesulfonamide (DNS-4NSBA) were synthesized as model haptens. When analysed by HPLC, a conjugate of DNS-4HABA and glutathione (GSH) with nucleophilic amino acids had two peaks (P-1 and P-2). FAB-MS and 1H-NMR revealed that the DNS-4HABA-GSH conjugate consisted of sulphinamide and semimercaptal. The reactivity of GSH to DNS-4ABA, DNS-4HABA and DNS-4NSBA was quantified by HPLC using an oxidization system (horseradish peroxidase/H2O2). The results show that production of DNS-4NSBA-GSH-conjugate was four to eight times higher than that of DNS-4HABA-GSH conjugate, but that DNS-4ABA did not bind with GSH. Skin reactions were assessed using guinea pigs, and strong delayed erythema was seen with DNS-4NSBA, which bound most strongly with GSH, whereas weak delayed erythema was seen with DNS-4ABA, which did not bind with GSH. This suggests a correlation between GSH conjugate production and skin reactions. DNS-4HABA enzymatically bound with proteins in rat and guinea pig liver cytosol and microsomal fractions. The proteins that bound to DNS-4HABA were purified by HPLC and then subjected to N-terminal amino acid analysis. Ubiquitin (10 kDa) and fatty acid binding protein (30 kDa) were detected in the rat liver cytosol fraction; retinol-dehydrogenase (35 kDa) in the rat microsomal fraction; and glutathione-S-transferase B (mmu) (25 kDa) in the guinea pig liver cytosol fraction. When DNS-4HABA or DNS-4NSBA binds to proteins that play important roles in the body, unexpected adverse reactions may occur. Furthermore, by utilizing our technique using model compounds, it may be possible to identify the carrier proteins of various compounds, including pharmaceutical agents.
Xenobiotica 2005 Sep
PMID:Antigenicity of sulfanilamide and its metabolites using fluorescent-labelled compounds. 1630 84


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