Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

3-Hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR), the key regulatory enzyme in the mevalonate (MVA) pathway, is rapidly degraded in mammalian cells supplemented with sterols or MVA. This accelerated turnover was blocked by N-acetyl-leucyl-leucyl-norleucinal (ALLN), MG-132, and lactacystin, and to a lesser extent by N-acetyl-leucyl-leucyl-methional (ALLM), indicating the involvement of the 26 S proteasome. Proteasome inhibition led to enhanced accumulation of high molecular weight polyubiquitin conjugates of HMGR and of HMGal, a chimera between the membrane domain of HMGR and beta-galactosidase. Importantly, increased amounts of polyubiquitinated HMGR and HMGal were observed upon treating cells with sterols or MVA. Cycloheximide inhibited the sterol-stimulated degradation of HMGR concomitantly with a marked reduction in polyubiquitination of the enzyme. Inhibition of squalene synthase with zaragozic acid blocked the MVA- but not sterol-stimulated ubiquitination and degradation of HMGR. Thus, similar to yeast, the ubiquitin-proteasome pathway is involved in the metabolically regulated turnover of mammalian HMGR. Yet, the data indicate divergence between yeast and mammals and suggest distinct roles for sterol and nonsterol metabolic signals in the regulated ubiquitination and degradation of mammalian HMGR.
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PMID:The ubiquitin-proteasome pathway mediates the regulated degradation of mammalian 3-hydroxy-3-methylglutaryl-coenzyme A reductase. 1096 18

Proteolysis by the ubiquitin-proteasome system is highly selective. Specificity is achieved by the cooperation of diverse ubiquitin-conjugating enzymes (Ubcs or E2s) with a variety of ubiquitin ligases (E3s) and other ancillary factors. These recognize degradation signals characteristic of their target proteins. In a previous investigation, we identified signals directing the degradation of beta-galactosidase and Ura3p fusion proteins via a subsidiary pathway of the ubiquitin-proteasome system involving Ubc6p and Ubc7p. This pathway has recently been shown to be essential for the degradation of misfolded and regulated proteins in the endoplasmic reticulum (ER) lumen and membrane, which are transported to the cytoplasm via the Sec61p translocon. Mutant backgrounds which prevent retrograde transport of ER proteins (hrd1/der3Delta and sec61-2) did not inhibit the degradation of the beta-galactosidase and Ura3p fusions carrying Ubc6p/Ubc7p pathway signals. We therefore conclude that the ubiquitination of these fusion proteins takes place on the cytosolic face of the ER without prior transfer to the ER lumen. The contributions of different sequence elements to a 16-amino-acid-residue Ubc6p-Ubc7p-specific signal were analyzed by mutation. A patch of bulky hydrophobic residues was an essential element. In addition, positively charged residues were found to be essential. Unexpectedly, certain substitutions of bulky hydrophobic or positively charged residues with alanine created novel degradation signals, channeling the degradation of fusion proteins to an unidentified proteasomal pathway not involving Ubc6p and Ubc7p.
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PMID:Degradation signals recognized by the Ubc6p-Ubc7p ubiquitin-conjugating enzyme pair. 1098 38

The ubiquitin-specific proteases (Ubps) are a family of largely dissimilar enzymes with two major conserved sequence regions, containing either a conserved cysteine residue or two conserved histidine residues, respectively. The murine Unp oncoprotein and its human homologue, Unph, both contain regions similar to the conserved Cys and His boxes common to all the Ubps. In this study we show that Unp and Unph are active deubiquitinating enzymes, being able to cleave ubiquitin from both natural and engineered linear ubiquitin-protein fusions, including the polyubiquitin precursor. Mutation of the conserved Unp Cys and His residues abolishes this activity, and identifies the likely His residue in the catalytic triad. Unp is tumorigenic when overexpressed in mice, leading to the suggestion that Unp may play a role in the regulation of ubiquitin-dependent protein degradation. We have demonstrated here that the high-level expression of Unp in yeast does not disrupt the degradation of the N-end rule substrate Tyr-beta-galactosidase (betagal), the non-N-end rule substrate ubiquitin-Pro-betagal, or the degradation of abnormal, canavanine-containing proteins. These data suggest that Unp is not a general modulator of ubiquitin-dependent proteolysis. However, Unp may have a role in the regulation of the degradation of a specific, as yet undescribed, substrate(s).
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PMID:Characterization of the ubiquitin-specific protease activity of the mouse/human Unp/Unph oncoprotein. 1101 21

A two-hybrid screen against an activation domain array of Saccharomyces cerevisiae proteins was carried out for 31 yeast proteasome proteins. Fifty-five putative interactions were identified: 21 between components of the proteasome complex and 34 between proteasome proteins and other proteins. Many of these latter interactions involved either proteins of the ubiquitin pathway, cell cycle proteins, protein kinases or a translation initiation factor subunit. The role of eleven proteins associated with proteasome function by these screens was analyzed by examining the corresponding deletion strains for temperature sensitivity and canavanine sensitivity and for the stability of a ubiquitin-beta-galactosidase fusion protein. These assays additionally implicated three proteins, Bim1, Ump1, and YKL171W, in proteasome function. This study demonstrates the utility of genome-wide two-hybrid assays as an entry point for the further analysis of a large protein complex.
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PMID:Two-hybrid analysis of the Saccharomyces cerevisiae 26S proteasome. 1159 89

UBP43 shows significant homology to well characterized ubiquitin-specific proteases and previously was shown to hydrolyze ubiquitin-beta-galactosidase fusions in Escherichia coli. In our assays, the activity of UBP43 toward Ub fusions was undetectable in vitro directing us to investigate the possibility of Ub-like proteins such as SUMO, Nedd8, and ISG15 as probable substrates. We consequently demonstrate that UBP43 can efficiently cleave only ISG15 fusions including native ISG15 conjugates linked via isopeptide bonds. In addition to commonly used methods we introduce a new experimental design featuring ISG15-UBP43 fusion self-processing. Deletion of the UBP43 gene in mouse leads to a massive increase of ISG15 conjugates in tissues indicating that UBP43 is a major ISG15-specific protease. UBP43 is the first bona fide ISG15-specific protease reported. Both ISG15 and UBP43 genes are known to be strongly induced by interferon, genotoxic stress, and viral infection. We postulate that UBP43 is necessary to maintain a critical cellular balance of ISG15-conjugated proteins in both healthy and stressed organisms.
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PMID:UBP43 (USP18) specifically removes ISG15 from conjugated proteins. 1178 88

The alpha1,2-mannosidase Mns1p involved in the N-glycosidic pathway in Saccharomyces cerevisiae is a type II membrane protein of the endoplasmic reticulum. The localization of Mns1p depends on retrieval from the Golgi through a mechanism that involves Rer1p. A chimera consisting of the transmembrane domain of Mns1p fused to the catalytic domain of the Golgi alpha1,2-mannosyltransferase Kre2p was localized in the endoplasmic reticulum of Deltapep4 cells and in the vacuoles of rer1/Deltapep4 by indirect immunofluorescence. The split-ubiquitin system was used to determine if there is an interaction between Mns1p and Rer1p in vivo. Co-expression of NubG-Mns1p and Rer1p-Cub-protein A-lexA-VP16 in L40 yeast cells resulted in cleavage of the reporter molecule, protein A-lexA-VP16, detected by western blot analysis and by expression of beta-galactosidase activity. Sec12p, another endoplasmic reticulum protein that depends on Rer1p for its localization, also interacted with Rer1p using the split-ubiquitin assay, whereas the endoplasmic reticulum protein Ost1p showed no interaction. A weak interaction was observed between Alg5p and Rer1p. These results demonstrate that the transmembrane domain of Mns1p is sufficient for Rer1p-dependent endoplasmic reticulum localization and that Mns1p and Rer1p interact. Furthermore, the split-ubiquitin system demonstrates that the C-terminal of Rer1p is in the cytosol.
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PMID:Interaction of the endoplasmic reticulum alpha 1,2-mannosidase Mns1p with Rer1p using the split-ubiquitin system. 1179 27

In eukaryotic cells, intracellular proteolysis occurs mainly via the ubiquitin-proteasome system. Expression of the yeast proteasome is under the control of the transcription factor, Rpn4p (also known as Son1p/Ufd5p). We show here that the RPN4 gene promoter contains regulatory sequences that bind Pdr1p and Pdr3p, two homologous zinc finger-containing transcription factors, which mediate multiple drug resistance through the expression of membrane transporter proteins. Mutations in the RPN4 Pdr1p/Pdr3p binding sites lead to decreased expression of the proteasome RPT6 gene and to defective ubiquitin-mediated proteolysis. Pdr3p, but not Pdr1p, is required for normal levels of intracellular proteolysis, indicating that the two transcription factors have distinct functions in the control of RPN4 expression. The RPN4 promoter contains an additional sequence that binds Yap1p, a bZIP-type transcription factor that plays an important role in the oxidative stress response and multidrug resistance. We also show that the Yap1p response element is important in the transactivation of RPN4 by Yap1p. In yeast cells lacking Pdr1p, ubiquitin-Pro-beta-galactosidase, a short-lived protein used to assay proteasome activity, is stabilized by the loss of Yap1p. These data demonstrate that the ubiquitin-proteasome system is controlled by transcriptional regulators of multidrug resistance via RPN4 expression.
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PMID:Control of 26S proteasome expression by transcription factors regulating multidrug resistance in Saccharomyces cerevisiae. 1191 14

Spinocerebellar ataxia type 1 (SCA1) is an autosomal-dominant neurodegenerative disorder characterized by ataxia and progressive motor deterioration. SCA1 has been known to associate with elongated polyglutamine tract in ataxin-1, the SCA1 gene product. Using the yeast two-hybrid system, we have found that USP7, a ubiquitin-specific protease, binds to ataxin-1. Further experiments with deletion mutants indicated that the C-terminal region of ataxin-1 was essential for the interaction. Liquid beta-galactosidase assay and coimmunoprecipitation experiments revealed that the strength of the interaction between USP7 and ataxin-1 is influenced by the length of the polyglutamine tract in the ataxin-1; weaker interaction was observed in mutant ataxin-1 with longer polyglutamine tract and USP7 was not recruited to the mutant ataxin-1 aggregates in the Purkinje cells of SCA1 transgenic mice. Our results suggest that altered function of the ubiquitin system can be involved in the pathogenesis of spinocerebellar ataxia type 1.
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PMID:USP7, a ubiquitin-specific protease, interacts with ataxin-1, the SCA1 gene product. 1209 61

Brain-derived neurotrophic factor (BDNF), one of the members of the nerve growth factor family of neurotrophins, is expressed in developing gustatory papillae and is thought to be the neurotrophin that supports gustatory innervation during development. BDNF expression does not cease after development but continues in some taste cells of adult mice. To determine which types of taste cells produce BDNF, we undertook an immunohistochemical study of taste cells in BDNF(LacZ) gene targeted "knock-in" adult mice. In these mice, beta-galactosidase (beta-gal) immunoreactivity is an indicator of cells that produce BDNF transcripts. In the tongues of adult BDNF(LacZ) mice, beta-gal (BDNF) is present in long slender taste cells, as well as pyriform taste cells. Bromodeoxyuridine labeling experiments in BDNF(LacZ) mice indicate that BDNF is not present in taste cells that are younger than 3 days postmitotic. BDNF mainly colocalizes with markers of type II and type III taste cells: ubiquitin carboxyl terminal hydrolase (PGP 9.5), serotonin (5-HT), neural cell adhesion molecule (N-CAM), synaptic associated protein of 25 kDa (SNAP-25), and to a lesser extent with alpha-gustducin. beta-Gal immunoreactivity is not associated with blood group H antigen, a marker of type I taste cells. We conclude that BDNF is absent from basal cells and type I (blood group H antigen immunoreactive) taste cells but is present in differentiated type II and type III taste cells. The presence of SNAP-25 in BDNF-expressing cells suggests a role for BDNF in synaptic formation and transmission.
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PMID:Brain-derived neurotrophic factor is present in adult mouse taste cells with synapses. 1262 64

We have identified and cloned 22 human cDNAs encoding novel members of the ubiquitin-specific protease (USP) family. Eighteen of the identified proteins contain all structural features characteristic of these cysteine proteinases, whereas four of them have been classified as non-peptidase homologues. Northern blot analysis demonstrated that the identified USPs are broadly and differentially distributed in human tissues, some of them being especially abundant in skeletal muscle or testis. Enzymatic studies performed with the identified USPs revealed that at least twelve of them are deubiquitylating enzymes based on their ability to cleave ubiquitin from a ubiquitin-beta-galactosidase fusion protein. These results provide additional evidence of the extreme complexity and diversity of the USP proteolytic system in human tissues and open the possibility to explore the relevance of their multiple components in the regulation of ubiquitin-mediated pathways in normal and pathological functions.
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PMID:Cloning and enzymatic analysis of 22 novel human ubiquitin-specific proteases. 1471 45


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