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)

The proteasome has been successfully targeted for the treatment of multiple myeloma and mantle cell lymphoma; however, in other hematologic malignancies, bortezomib has been less effective as a single agent. Here, we describe effects of NPI-0052, a novel proteasome inhibitor, in leukemia model systems. In cell lines, NPI-0052 inhibits all 3 proteolytic activities associated with the proteasome: chymotrypsin-, trypsin-, and caspase-like. NPI-0052 also induces DNA fragmentation in leukemia lines and in mononuclear cells from a Ph + acute lymphoblastic leukemia (ALL) patient. Caspase-3 activation by NPI-0052 was seen in wild-type Jurkat cells, but was significantly lessened in Fas-associated death domain (FADD)-deficient or caspase-8-deficient counterparts. NPI-0052-induced apoptosis was further probed using caspase-8 inhibitors, which were more protective than caspase-9 inhibitors. N-acetyl cysteine (NAC) also conferred protection against NPI-0052-induced apoptosis, indicating a role for oxidative stress by NPI-0052. In support of the drug's in vitro activities, biweekly treatment with NPI-0052 lessened total white blood cell (WBC) burden over 35 days in leukemic mice. Interestingly, combining NPI-0052 with either MS-275 or valproic acid (VPA) induced greater levels of cell death than the combination of bortezomib with these histone deacetylase inhibitors (HDACi). These effects of NPI-0052, alone and in combination with HDACi, warrant further testing to determine the compound's clinical efficacy in leukemia.
...
PMID:NPI-0052, a novel proteasome inhibitor, induces caspase-8 and ROS-dependent apoptosis alone and in combination with HDAC inhibitors in leukemia cells. 1735 34

Pristimerin is a natural product derived from the Celastraceae and Hippocrateaceae families that were used as folk medicines for anti inflammation in ancient times. Although it has been shown that pristimerin induces apoptosis in breast cancer cells, the involved mechanism of action is unknown. The purpose of the current study is to investigate the primary target of pristimerin in human cancer cells, using prostate cancer cells as a working model. Nucleophilic susceptibility and in silico docking studies show that C6 of pristimerin is highly susceptible towards a nucleophilic attack by the hydroxyl group of N-terminal threonine of the proteasomal chymotrypsin subunit. Consistently, pristimerin potently inhibits the chymotrypsin-like activity of a purified rabbit 20S proteasome (IC50 2.2 micromol/L) and human prostate cancer 26S proteasome (IC50 3.0 micromol/L). The accumulation of ubiquitinated proteins and three proteasome target proteins, Bax, p27 and I kappa B-alpha, in androgen receptor (AR)-negative PC-3 prostate cancer cells supports the conclusion that proteasome inhibition by pristimerin is physiologically functional. This observed proteasome inhibition subsequently led to the induction of apoptotic cell death in a dose- and kinetic-dependent manner. Furthermore, in AR-positive, androgen-dependent LNCaP and AR-positive, androgen-independent C4-2B prostate cancer cells, proteasome inhibition by pristimerin results in suppression of AR protein prior to apoptosis. Our data demonstrate, for the first time, that the proteasome is a primary target of pristimerin in prostate cancer cells and inhibition of the proteasomal chymotrypsin-like activity by pristimerin is responsible for its cancer cell death-inducing property.
...
PMID:Pristimerin induces apoptosis by targeting the proteasome in prostate cancer cells. 1754 80

The effects of cadmium (Cd) on cellular proteolytic responses were investigated in the roots and leaves of tomato (Solanum lycopersicum L., var Ibiza) plants. Three-week-old plants were grown for 3 and 10 days in the presence of 0.3-300 microM Cd and compared to control plants grown in the absence of Cd. Roots of Cd treated plants accumulated four to fivefold Cd as much as mature leaves. Although 10 days of culture at high Cd concentrations inhibited plant growth, tomato plants recovered and were still able to grow again after Cd removal. Tomato roots and leaves are not modified in their proteolytic response with low Cd concentrations (< or =3 microM) in the incubation medium. At higher Cd concentration, protein oxidation state and protease activities are modified in roots and leaves although in different ways. The soluble protein content of leaves decreased and protein carbonylation level increased indicative of an oxidative stress. Conversely, protein content of roots increased from 30 to 50%, but the amount of oxidized proteins decreased by two to threefold. Proteolysis responded earlier in leaves than in root to Cd stress. Additionally, whereas cysteine- and metallo-endopeptidase activities, as well as proteasome chymotrypsin activity and subunit expression level, increased in roots and leaves, serine-endopeptidase activities increased only in leaves. This contrasted response between roots and leaves may reflect differences in Cd compartmentation and/or complexation, antioxidant responses and metabolic sensitivity to Cd between plant tissues. The up-regulation of the 20S proteasome gene expression and proteolytic activity argues in favor of the involvement of the 20S proteasome in the degradation of oxidized proteins in plants.
...
PMID:Modifications in endopeptidase and 20S proteasome expression and activities in cadmium treated tomato (Solanum lycopersicum L.) plants. 1795 56

Oxidative injury has been found to be associated with proteasomal inactivity. In this study, the extent of oxidative damage and its effects on proteasomal function has been critically assessed. Left anterior descending coronary artery was occluded (ischemia) and reperfused with or without preconditioning in male Sprague-Dawley rats. For further validation, H9c2 cardiac myoblasts cultures were used. We demonstrate that ischemia-reperfusion causes extensive endoplasmic reticulum stress as evident from the degradation of GRP78 transcript followed by its rapid induction. Western blot analysis and immunohistochemistry showed that increasing duration of ischemia and reperfusion causes accumulation of phosphorylated IkappaB (p-IkappaB), thereby suggesting proteasomal inactivity. However, similar analysis for Nrf2, a key mediator of antioxidant defense, showed sustained activation, suggesting intact proteasomal function. Preconditioning of the myocardium preserves the degradation of p-IkappaB, suggesting effective functioning of proteasome after preconditioning. Further analysis with specific proteosomal inhibitors like epoxomicin (100 nM, inhibits chymotrypsin-like activities of proteasomes) and lactacystin (2 microM, inhibits chymotrypsin as well as some trypsin-like activities of proteasomes) suggests that degradation of p-IkappaB and Keap-1 in the proteasome occurs by independent mechanisms. This study gives further insight into interrelationship between oxidative injury and catalytic function of the proteasome in heart, where oxidative injury causes selective rather than global inhibition of proteasome.
...
PMID:Oxidative injury induces selective rather than global inhibition of proteasomal activity. 1807 53

The 20S proteasome of eukaryotic cells has at least three distinct peptidase activities (trypsin-like, chymotrypsin-like and peptidylglutamylpeptide (PGP) hydrolase activities). These peptidases are latent and require appropriate activators. SDS has been widely used as an activator of these peptidases, but the mechanism of its activation remains unresolved. In this study, we investigated the kinetics of the SDS-activated hydrolysis of the above three types of peptidase of the 20S proteasome purified from Xenopus oocytes. When the reaction was started by simultaneous adding both SDS and substrate, maximal rates of hydrolysis were reached after appreciable lag phases with the trypsin-type substrate [t-butyloxycarbonylLeu-Arg-Arg-4-methylcoumaryl-7-amide (Boc-LRR-MCA)], but no such lag phases were observed with the chymotrypsin-type and PGP hydrolase-type substrates [succinyl-Leu-Leu-Val-Tyr-4-methylcoumaryl-7-amide (Suc-LLVY-MCA), and benzyloxycarbonyl-Leu-Leu-Glu-2-naphthylamide (Cbz-LLE-2NA), respectively]. Similarly, changes in the hydrolysis rate to a reduced level upon dilution of SDS occurred after an appreciable lag phase again in the trypsin-like peptidase, but not in the other types. The lag phase characteristic of the trypsin-like peptidase was dependent on the substrate concentration. Thus, the lag phase was less discernible at very low concentrations of the substrate (e.g. at concentrations in the order of 1/100 of the Km value), but became more conspicuous with the increases in the substrate concentration. This lag phase also vanished upon preincubation of the activator (SDS) for a short period of 5 sec. These results suggest that the formation of the enzyme-substrate complex in the trypsin-like reaction induces a conformational change in the enzyme which makes the SDS activator site(s) in an occluded form, reducing the rates of SDS binding and dissociation.
...
PMID:Activation of the 20S Proteasome of Xenopus Oocytes by SDS: Evidence for the Substrate-Induced Conformational Change Characteristic of Trypsin-Like Peptidase. 1846 98

The 20 S proteasomes play a critical role in intracellular homeostasis and stress response. Their function is tuned by covalent modifications, such as phosphorylation. In this study, we performed a comprehensive characterization of the phosphoproteome for the 20 S proteasome complexes in both the murine heart and liver. A platform combining parallel approaches in differential sample fractionation (SDS-PAGE, IEF, and two-dimensional electrophoresis), enzymatic digestion (trypsin and chymotrypsin), phosphopeptide enrichment (TiO(2)), and peptide fragmentation (CID and electron transfer dissociation (ETD)) has proven to be essential for identifying low abundance phosphopeptides. As a result, a total of 52 phosphorylation identifications were made in mammalian tissues; 44 of them were novel. These identifications include single (serine, threonine, and tyrosine) and dual phosphorylation peptides. 34 phosphopeptides were identified by CID; 10 phosphopeptides, including a key modification on the catalytically essential beta5 subunit, were identified only by ETD; eight phosphopeptides were shared identifications by both CID and ETD. Besides the commonly shared phosphorylation sites, unique sites were detected in the murine heart and liver, documenting variances in phosphorylation between tissues within the proteasome populations. Furthermore the biological significance of these 20 S phosphoproteomes was evaluated. The role of cAMP-dependent protein kinase A (PKA) to modulate these phosphoproteomes was examined. Using a proteomics approach, many of the cardiac and hepatic 20 S subunits were found to be substrate targets of PKA. Incubation of the intact 20 S proteasome complexes with active PKA enhanced phosphorylation in both existing PKA phosphorylation sites as well as novel sites in these 20 S subunits. Furthermore treatment with active PKA significantly elevated all three peptidase activities (beta1 caspase-like, beta2 trypsin-like, and beta5 chymotrypsin-like), demonstrating a functional role of PKA in governing these 20 S phosphoproteomes.
...
PMID:Revealing the dynamics of the 20 S proteasome phosphoproteome: a combined CID and electron transfer dissociation approach. 1857 62

Oligo-arginines are cell-penetrating peptides and find use as carriers for transportation of various membrane-impermeable biopharmaceuticals into target cells. We have found that oligo-arginines of a length of 4-10 amino acids, but especially (Arg)(8), are able to inhibit the major intracellular proteolytic system, the proteasome, with mixed-type inhibition characteristics. The IC(50) values of (Arg)(8) for the proteasomal chymotrypsin-like and caspase-like activities are approximately 100 and 200 nM, respectively. The inhibition of the trypsin-like activity never exceeds 50% even at micromolar concentrations. (Arg)(8) also inhibits 20S proteasome/PA28 complexes as well as 26S proteasomes, although with a decreased efficiency. Due to its cell membrane-penetrating capability, incubation of HeLa cells in the presence of (Arg)(8) resulted in an impaired activity of proteasomes going along with an accumulation of high-molecular mass ubiquitin-conjugated proteins, the preferred substrates of 26S proteasomes. The in vivo susceptibility of the three proteasome activities resembles that found in vitro with chymotrypsin-like>caspase-like>trypsin-like activities. Since inhibition of the proteasome system might affect fundamental basic cellular processes but on the other side might also prevent the degradation of a proteinacous cargo, we suggest that this proteasome inhibitory activity should be taken into account when oligo-arginines are being considered for use as vectors for the intracellular delivery of pharmaceuticals.
...
PMID:The cell-penetrating peptide octa-arginine is a potent inhibitor of proteasome activities. 1902 53

It is well established that nitric oxide (NO) inhibits vascular smooth muscle cell (VSMC) proliferation by modulating cell cycle proteins. The 26S proteasome is integral to protein degradation and tightly regulates cell cycle proteins. Therefore, we hypothesized that NO directly inhibits the activity of the 26S proteasome. The three enzymatic activities (chymotrypsin-like, trypsin-like and caspase-like) of the 26S proteasome were examined in VSMC. At baseline, caspase-like activity was approximately 3.5-fold greater than chymotrypsin- and trypsin-like activities. The NO donor S-nitroso-N-acetylpenicillamine (SNAP) significantly inhibited all three catalytically active sites in a time- and concentration-dependent manner (P<0.05). Caspase-like activity was inhibited to a greater degree (77.2% P<0.05). cGMP and cAMP analogs and inhibitors had no statistically significant effect on basal or NO-mediated inhibition of proteasome activity. Dithiothreitol, a reducing agent, prevented and reversed the NO-mediated inhibition of the 26S proteasome. Nitroso-cysteine analysis following S-nitrosoglutathione exposure revealed that the 20S catalytic core of the 26S proteasome contains 10 cysteines which were S-nitrosylated by NO. Evaluation of 26S proteasome subunit protein expression revealed differential regulation of the alpha and beta subunits in VSMC following exposure to NO. Finally, immunohistochemical analysis of subunit expression revealed distinct intracellular localization of the 26S proteasomal subunits at baseline and confirmed upregulation of distinct subunits following NO exposure. In conclusion, NO reversibly inhibits the catalytic activity of the 26S proteasome through S-nitrosylation and differentially regulates proteasomal subunit expression. This may be one mechanism by which NO exerts its effects on the cell cycle and inhibits cellular proliferation in the vasculature.
...
PMID:Nitric oxide regulates the 26S proteasome in vascular smooth muscle cells. 1923 5

The amide hydrogens that are exposed to solvent in the high-resolution X-ray structures of ubiquitin, FK506-binding protein, chymotrypsin inhibitor 2, and rubredoxin span a billion-fold range in hydroxide-catalyzed exchange rates which are predictable by continuum dielectric methods. To facilitate analysis of transiently accessible amides, the hydroxide-catalyzed rate constants for every backbone amide of ubiquitin were determined under near physiological conditions. With the previously reported NMR-restrained molecular dynamics ensembles of ubiquitin (PDB codes 2NR2 and 2K39 ) used as representations of the Boltzmann-weighted conformational distribution, nearly all of the exchange rates for the highly exposed amides were more accurately predicted than by use of the high-resolution X-ray structure. More strikingly, predictions for the amide hydrogens of the NMR relaxation-restrained ensemble that become exposed to solvent in more than one but less than half of the 144 protein conformations in this ensemble were almost as accurate. In marked contrast, the exchange rates for many of the analogous amides in the residual dipolar coupling-restrained ubiquitin ensemble are substantially overestimated, as was particularly evident for the Ile 44 to Lys 48 segment which constitutes the primary interaction site for the proteasome targeting enzymes involved in polyubiquitylation. For both ensembles, "excited state" conformers in this active site region having markedly elevated peptide acidities are represented at a population level that is 10(2) to 10(3) above what can exist in the Boltzmann distribution of protein conformations. These results indicate how a chemically consistent interpretation of amide hydrogen exchange can provide insight into both the population and the detailed structure of transient protein conformations.
...
PMID:Peptide conformer acidity analysis of protein flexibility monitored by hydrogen exchange. 1972 80

Parkin suppression induces accumulation of beta-amyloid in mutant tau mice. We studied the effect of parkin suppression on behaviour and brain pathology in APP(swe) mutant mice. We produced double mutant mice with human mutated APP(swe)+partial (hemizygote) or total (homozygote) deletion of Park-2 gene. We studied the development, behaviour, brain histology, and biochemistry of 12- and 16-month-old animals in 6 groups of mice, with identical genetic background: wild-type (WT), APP(swe) overexpressing (APP), hemizygote and homozygote deletion of Park-2 (PK(+/-) and PK(-/-), respectively), and double mutants (APP/PK(+/-) and APP/PK(-/-)). APP mice have reduced weight gain, decreased motor activity, and reduced number of entrances and of arm alternation in the Y-maze, abnormalities which were partially or completely normalized in APP/PK(+/-) and APP/PK(-/-) mice. The double mutants had similar number of mutant human APP transgene copies than the APP and levels of 40 and 80 kDa proteins; but both of them, APP/PK(+/-) and APP/PK(-/-) mice, had less plaques in cortex and hippocampus than the APP mice. APP mutant mice had increased apoptosis, proapoptotic Bax/Bcl2 ratios, and gliosis, but these death-promoting factors were normalized in APP/PK(+/-) and APP/PK(-/-) mice. APP mutant mice had an increased number of tau immunoreactive neuritic plaques in the cerebral cortex as well as increased levels of total and phosphorylated tau protein, and these changes were partially normalized in APP/PK(+/-) heterozygotic and homozygotic APP/PK(-/-) mice. Compensatory protein-degrading systems such as HSP70, CHIP, and macroautophagy were increased in APP/PK(+/-) and APP/PK(-/-). Furthermore, the chymotrypsin- and trypsin-like proteasome activities, decreased in APP mice in comparison with WT, were normalized in the APP/PK(-/-) mice. We proposed that partial and total suppression of parkin triggers compensatory mechanisms, such as chaperone overexpression and increased autophagy, which improved the behavioural and cellular phenotype of APP(swe) mice.
...
PMID:The effects of parkin suppression on the behaviour, amyloid processing, and cell survival in APP mutant transgenic mice. 1981 12


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

---