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

---

Query: EC:3.4.25.1 (proteasome)
28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To explore membrane-permeable synthetic inhibitors that discriminate between endogenous calpain and proteasome in cells, we examined the inhibition of profiles against calpain and proteasome in vitro and in vivo of peptidyl aldehydes possessing di-leucine and tri-leucine. The tripeptide aldehyde benzyloxycarbonyl-leucyl-leucinal (ZLLLal) strongly inhibited calpain and proteasome activities in vitro. The concentration required for 50% inhibition (IC50) of the casein-degrading activity of calpain was 1.25 microM, and the IC50s for the succinyl-leucyl-leucyl-valyl-tyrosine-4-methylcoumaryl-7-amide (Suc-LLVY-MCA)- and benzyloxycarbonyl-leucyl-leucyl-leucine-4-methylcoumaryl -7-amide (ZLLL-MCA)-degrading activities of proteasome were 850 and 100 nM, respectively. On the other hand, the synthetic dipeptide aldehyde benzyloxycarbonyl-leucyl-leucinal (ZLLal) strongly inhibited the casein degrading activity of calpain (IC50 1.20 microM), but the inhibition of proteasome was weak (IC50S for SucLLVY-MCA- and ZLLL-MCA-degrading activities were 120 and 110 microM, respectively). Thus, while calpain was inhibited by similar concentrations of ZLLal and ZLLLal, the inhibitory potencies of ZLLLal against the ZLLL-MCA- and Suc-LLVY-MCA-degrading activities in proteasome were 1,100 and 140 times stronger than those of ZLLal, respectively. To evaluate the effectiveness of these inhibitors on intracellular proteasome, the induction of neurite outgrowth in PC12 cells caused by proteasome inhibition was examined. ZLLLal and ZLLal initiated neurite outgrowth with optimal concentrations of 20 nM and 10 microM, respectively, again showing a big difference in the effective concentrations for the proteasome inhibition as in vitro. As for the effect on intracellular calpain, the concentration of ZLLLal and ZLLal required for the inhibition of the autolytic activation of calpain in rabbit erythrocytes were 100 and 100 microM or more, respectively. The almost equal inhibitory potencies of ZLLLal and ZLLal were in agreement with the inhibition of calpain in vitro. These differential effects of inhibitors against calpain and proteasome are potentially useful for identifying the functions of calpain and proteasome in cell physiology and pathology.
...
PMID:Differential inhibition of calpain and proteasome activities by peptidyl aldehydes of di-leucine and tri-leucine. 883 56

Point mutations occurring within the Cu/Zn superoxide dismutase (SOD1) gene have been implicated in the etiology of some cases of familial amyotrophic lateral sclerosis (FALS). In order to better understand the functional consequences of these mutations, we have introduced FALS mutations into the mouse SOD1 gene and studied the expression of the mutant templates in stably transformed cell lines. Pulse-chase analyses of lysates derived from cell lines stably expressing the Cu/Zn SOD isoforms indicate that the FALS mutant Cu/Zn SOD proteins are turned over more rapidly than wild-type SOD. Protease inhibitors specific for the major intracellular proteolytic activities were used to characterize the degradative pathways involved in the turnover of mutant Cu/Zn SOD. Inhibition of the chymotrypsin-like activity of the proteasome (also known as multicatalytic proteinase or ubiquitin, ATP-dependent proteinase) by a synthetic dipeptide aldehyde led to a significant increase in levels of the mutant Cu/Zn SOD implicating this proteolytic pathway in the turnover of the FALS mutant SOD proteins.
...
PMID:Proteasome inhibition enhances the stability of mouse Cu/Zn superoxide dismutase with mutations linked to familial amyotrophic lateral sclerosis. 883 67

The multicatalytic proteinase complex or 20S proteasome is involved in the extralysosomal degradation of both long- and short-lived proteins. The eukaryotic enzyme is composed of 14 nonidentical subunits arranged as a complex dimer of the composition (alpha7beta7)2. Recent studies identify N-terminal threonines present on some beta-subunits as the active-site residues. It has been proposed that the molecule contains three or four proteolytically active subunits [Seemuller et al., Science 268, 579-582 (1995)]. Studies with synthetic substrates, activators, and inhibitors, however, have identified at least five distinct catalytic activities. To further characterize the specificity of the previously defined "peptidyl glutamyl peptide bond hydrolyzing activity," N-benzyloxycarbonyl-Leucyl-Leucyl-Glutamal was synthesized as a potential inhibitor. Surprisingly, this aldehyde most potently inhibited the "branched chain amino acid preferring activity" (BrAAP). To further explore BrAAP specificity, novel substrates containing internal prolyl and glutamyl residues were synthesized. Their use established that the BrAAP activity catalyzed both a postproline and a postglutamate cleavage and therefore has a broader specificity than previously recognized. These results help explain earlier observations on treatment of the multicatalytic proteinase complex with 3,4-dichloroisocoumarin. This reagent activates both the BrAAP activity and the degradation of beta-casein and inhibits the other catalytic activities.
...
PMID:Cleavage of Pro-X and Glu-X bonds catalyzed by the branched chain amino acid preferring activity of the bovine pituitary multicatalytic proteinase complex (20S proteasome). 883 46

Rb protein is a critical regulator of entry into the cell cycle, and loss of Rb function by deletions, mutations, or interaction with DNA viral oncoproteins leads to oncogenic transformation. We have shown that the human papilloma virus (HPV)-16 E7 gene is sufficient to induce the immortalization of mammary epithelial cells (MECs). Surprisingly, the steady-state level of Rb protein in these immortal cells was drastically decreased. Here, we used pulse-chase analysis to show that the in vivo loss of Rb protein in E7-immortalized MECs is a consequence of enhanced degradation. Expression of HPV16 E7 in a cell line with a temperature-sensitive mutation in the E1 enzyme of the ubiquitin pathway demonstrated that degradation of Rb was ubiquitin dependent. Treatment of E7-immortalized MECs with aldehyde inhibitors of proteasome-associated proteases led to a marked stabilization of Rb protein, particularly the hypophosphorylated form. Taken together, our results provide evidence for HPV-16 E7-induced enhanced degradation of Rb protein via a ubiquitin-proteasome pathway and suggest a second mechanism of oncogenic transformation by E7, in addition to its previously identified ability to sequester Rb from E2F. Our analyses also show that normal Rb levels are regulated by the ubiquitin-proteasome degradation pathway.
...
PMID:E7 protein of human papilloma virus-16 induces degradation of retinoblastoma protein through the ubiquitin-proteasome pathway. 884 Sep 74

Recent studies have suggested that activation of the ubiquitin-proteasome pathway is primarily responsible for the rapid loss of muscle proteins in various types of atrophy. The present studies were undertaken to test if different classes of muscle proteins are degraded by this pathway. In extracts of rabbit psoas muscle, the complete degradation of soluble proteins to amino acids was stimulated up to 6-fold by ATP. Peptide aldehyde inhibitors of the proteasome or the removal of proteasomes markedly inhibited only the ATP-dependent process. Addition of purified myosin, actin, troponin, or tropomyosin to these extracts showed that these proteins served as substrates for the ubiquitin-proteasome pathway. By contrast, degradation of myoglobin did not require ATP, proteasomes, or any known proteases in muscles. When myosin, actin, and troponin were added as actomyosin complexes or as intact myofibrils to these extracts, they were not hydrolyzed at a significant rate, probably because in these multicomponent complexes, these proteins are protected from degradation. Accordingly, actin (but not albumin or troponin) inhibited the degradation of 125I-myosin, and actin was found to selectively inhibit ubiquitin conjugation to 125I-myosin. Also, the presence of tropomyosin inhibited the degradation of 125I-troponin. However, neither actin nor tropomyosin inhibited the degradation of 125I-lysozyme or soluble muscle proteins. Thus, specific interactions between the myofibrillar proteins appear to protect them from ubiquitin-dependent degradation, and the rate-limiting step in their degradation is probably their dissociation from the myofibril.
...
PMID:Importance of the ATP-ubiquitin-proteasome pathway in the degradation of soluble and myofibrillar proteins in rabbit muscle extracts. 890 Jan 46

We have studied whether various agents that inhibit purified yeast and mammalian 26 S proteasome can suppress the breakdown of different classes of proteins in Saccharomyces cerevisiae. The degradation of short-lived proteins was inhibited reversibly by peptide aldehyde inhibitors of proteasomes, carbobenzoxyl-leucinyl-leucinyl-leucinal (MG132) and carbobenzoxyl-leucinyl-leucinyl-norvalinal (MG115), in a yeast mutant with enhanced permeability, but not in wild-type strains. Lactacystin, an irreversible proteasome inhibitor, had no effect, but the beta-lactone derivative of lactacystin, which directly reacts with proteasomes, inhibited the degradation of short-lived proteins. These inhibitors also blocked the rapid ubiquitin-dependent breakdown of a beta-galactosidase fusion protein and caused accumulation of enzymatically active molecules in cells. The degradation of the bulk of cell proteins, which are long-lived molecules, was not blocked by proteasome inhibitors, but could be blocked by phenylmethylsulfonyl fluoride. This agent, which inhibits multiple vacuolar proteases, did not affect the proteasome or breakdown of short-lived proteins. These two classes of inhibitors can thus be used to distinguish the cytosolic and vacuolar proteolytic pathways and to increase the cellular content of short-lived proteins.
...
PMID:Selective inhibitors of the proteasome-dependent and vacuolar pathways of protein degradation in Saccharomyces cerevisiae. 891 Mar 2

A prominent feature of the life cycle of intracellular parasites is the profound morphological changes they undergo during development in the vertebrate and invertebrate hosts. In eukaryotic cells, most cytoplasmic proteins are degraded in proteasomes. Here, we show that the transformation in axenic medium of trypomastigotes of Trypanosoma cruzi into amastigote-like organisms, and the intracellular development of the parasite from amastigotes into trypomastigotes, are prevented by lactacystin, or by a peptide aldehyde that inhibits proteasome function. Clasto-lactacystin, an inactive analogue of lactacystin, and cell-permeant peptide aldehyde inhibitors of T. cruzi cysteine proteinases have no effect. We have also identified the 20S proteasomes from T. cruzi as a target of lactacystin in vivo. Our results document the essential role of proteasomes in the stage-specific transformation of a protozoan.
...
PMID:Proteasome activity is required for the stage-specific transformation of a protozoan parasite. 892 Aug 78

HeLa cells growing in vitro were treated with the peptidyl aldehyde inhibitor of the chymotrypsin-like activity of the proteasome N-benzyloxycarbonyl-Ile-Glu(O-t-butyl)-Ala-leucinal (PSI). Immunofluorescence studies of treated cells revealed the formation of massive perinuclear aggregates rich in ubiquitin and proteasomal antigens, which on the ultrastructural level appeared as perinuclear aggregates of electron-dense material, usually in the vicinity of Golgi cisternae. Histochemical studies disclosed that these cells contained protein-rich perinuclear aggregates detected by amido black staining, while unusual accumulations of lipids, carbohydrates, or nucleic acids were not present. Inhibition of protein synthesis by cycloheximide prevented the formation of aggregates, whereas microtubule disruption by nocodazole induced a dispersion of the aggregates. We hypothesize that aggregates induced by PSI treatment correspond to accumulations of proteasome-substrate complexes in a well-defined region, where the proteolytic processes of the ubiquitin-proteasome pathway seem to be somehow centered. We propose to call this region the proteolysis center.
...
PMID:Ubiquitin-mediated proteolysis centers in HeLa cells: indication from studies of an inhibitor of the chymotrypsin-like activity of the proteasome. 892 70

We evaluated the possibility that distinct proteolytic pathways contribute to the down-regulation of a novel (epsilon) or conventional (alpha) isoform of protein kinase C (PKC) in nonimmortalized human fibroblasts. Inhibitors of calpains and other cysteine proteinases, vesicle trafficking, or lysosomal proteolysis did not affect the down-regulation of PKC-alpha or -epsilon produced by bryostatin 1 (Bryo). Lactacystin (Lacta) and certain terminal aldehyde tripeptides or tetrapeptides, which selectively inhibit the proteasome, preserved substantial PKC-alpha and -epsilon protein from down-regulation by Bryo or phorbol-12-myristate-13-acetate. Lacta preserved active kinase in vivo, as shown by the retention of Bryo-induced autophosphorylated PKC-alpha. Concomitant with down-regulation, Bryo produced PKC-alpha and -epsilon species that were larger than the native proteins (80 and 90 kDa, respectively). Western blot analysis showed that the larger PKC-alpha species were ubiquitinylated. Treatment with Bryo plus Lacta synergistically increased multiubiquitinylated PKC-alpha, as expected if Bryo induces ubiquitinylation of PKC-alpha and Lacta blocks its degradation. Bryo also produced a 76-kDa, nonphosphorylated form of PKC-alpha and an 86-kDa form of PKC-epsilon. Phosphatase inhibitors decreased production of 76- and 86-kDa PKC-alpha and -epsilon by Bryo and preserved 80- and 90-kDa PKC-alpha and -epsilon, respectively. Our results suggest that the down-modulation of PKC-alpha and -epsilon occurs principally via the ubiquitin/ proteasome pathway. Dephosphorylation seems to predispose PKC to ubiquitinylation.
...
PMID:Bryostatin 1 and phorbol ester down-modulate protein kinase C-alpha and -epsilon via the ubiquitin/proteasome pathway in human fibroblasts. 905 99

Pathways for presenting proteins from the extracellular fluids on MHC class I molecules have been described in macrophages. However, it is uncertain whether similar mechanisms exist in dendritic cells, because conventional preparations of these cells can be contaminated with macrophages. We addressed this issue by transducing granulocyte-macrophage CSF into bone marrow cultures followed by supertransfection with myc and raf oncogenes. These immortalized clones displayed dendritic morphology, and many expressed the dendritic cell-specific markers DEC-205 and 33D1 as well as high levels of MHC molecules and costimulatory molecules. Using these cloned dendritic cells, we found that exogenous OVA could be presented on both their MHC class I and class II molecules. This presentation was markedly enhanced when the Ag was particulate and internalized by phagocytosis. Presentation of particulate OVA on MHC class I molecules was insensitive to the weak base chloroquine, but was blocked by peptide aldehyde inhibitors of the proteasome, indicating that the class I-presented peptides were generated in the cytosol. Brefeldin A, which inhibits the exocytosis of newly synthesized proteins from the endoplasmic reticulum, also inhibited Ag presentation. These results establish that dendritic cells can present exogenous Ags on MHC class I molecules and appear to use a similar phagosome to cytosol pathway as macrophages. Therefore, dendritic cells are likely to play an important role in generating immune responses to tissue transplants and tumors in vivo. Furthermore, these findings provide an approach for targeting vaccine Ags into these cells to prime immune responses in vivo.
...
PMID:Cloned dendritic cells can present exogenous antigens on both MHC class I and class II molecules. 905 6


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---