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)

Recent studies have revealed that rabbit reticulocyte lysate (RRL) efficiently reconstitutes endoplasmic reticulum-associated degradation (ERAD) of mutant and misfolded membrane proteins. When supplemented with canine pancreas microsomal membranes, the RRL system faithfully carries out ER targeting, translocation, glycosylation, and membrane integration events and therefore provides a ready source of 35S-labeled protein with defined transmembrane topology. These substrates can be rapidly isolated in native ER membranes which, when incubated in RRL lacking exogenous hemin, are degraded in an ATP-dependent manner by the ubiquitin-proteasome pathway. Because the newly translated protein is the only source of radiolabel, degradation can be followed to its end state by conversion into trichloroacetic acid (TCA)-soluble peptide fragments. A particularly useful aspect of this system is that both membrane-associated and cytosolic components are amenable to biochemical and pharmacological manipulation. Here we describe techniques for preparing translation- and degradation-competent RRL, affinity depletion, identification of cytosolic factors involved in degrading the cystic fibrosis transmembrane conductance regulator (CFTR), and reconstitution of ERAD by add-back of purified recombinant proteins. These techniques provide a powerful tool for dissecting components involved in ubiquitination, degradation, and in particular, extraction of transmembrane ERAD substrates.
...
PMID:Reticulocyte lysate as a model system to study endoplasmic reticulum membrane protein degradation. 1591 33

In contrast with the accelerated degradation observed in tumor cells in response to sterols, hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase turnover in whole animals was not increased by dietary cholesterol. Furthermore, treating rats with lovastatin to lower hepatic cholesterol levels did not decrease the rate of degradation. The half-life remained in the 6 h range. Co-immunoprecipitation studies revealed that the amount of ubiquitin associated with the reductase was entirely dependent upon the amount of microsomal protein subjected to immunoprecipitation. The results indicate that in liver, neither the rate of reductase protein degradation nor the ubiquitin-proteasome system appear to play roles in mediating changes in HMG-CoA reductase protein levels in response to dietary cholesterol.
...
PMID:Degradation of HMG-CoA reductase in rat liver is cholesterol and ubiquitin independent. 1591 82

Misfolded secretory proteins are transported across the endoplasmic reticulum (ER) membrane into the cytosol for degradation by proteasomes. A large fraction of proteasomes in a cell is associated with the ER membrane. We show here that binding of proteasomes to ER membranes is salt sensitive, ATP dependent, and mediated by the 19S regulatory particle. The base of the 19S particle, which contains six AAA-ATPases, binds to microsomal membranes with high affinity, whereas the 19S lid complex binds weakly. We demonstrate that ribosomes and proteasomes compete for binding to the ER membrane and have similar affinities for their receptor. Ribosomes bind to the protein conducting channel formed by the Sec61 complex in the ER membrane. We co-precipitated subunits of the Sec61 complex with ER-associated proteasome 19S particles, and found that proteoliposomes containing only the Sec61 complex retained proteasome binding activity. Collectively, our data suggest that the Sec61 channel is a principal proteasome receptor in the ER membrane.
...
PMID:The protein translocation channel binds proteasomes to the endoplasmic reticulum membrane. 1597 33

Insulin induces and dietary n-3 PUFAs suppress hepatic de novo lipogenesis by controlling sterol-regulatory element binding protein-1 nuclear abundance (nSREBP-1). Our goal was to define the mechanisms involved in this regulatory process. Insulin treatment of rat primary hepatocytes rapidly augments nSREBP-1 and mRNA(SREBP-1c) while suppressing mRNA(Insig-2) but not mRNA(Insig-1). These events are preceded by rapid but transient increases in Akt and Erk phosphorylation. Removal of insulin from hepatocytes leads to a rapid decline in nSREBP-1 [half-time (T1/2) approximately 10 h] that is abrogated by inhibitors of 26S proteasomal degradation. 22:6,n-3, the major n-3 PUFA accumulating in livers of fish oil-fed rats, suppresses hepatocyte levels of nSREBP-1, mRNA(SREBP-1c), and mRNA(Insig-2) but modestly and transiently induces mRNA(Insig-1). More importantly, 22:6,n-3 accelerates the disappearance of hepatocyte nSREBP-1 (T1/2 approximately 4 h) through a 26S proteasome-dependent process. 22:6,n-3 has minimal effects on microsomal SREBP-1 and sterol-regulatory element binding protein cleavage-activating protein or nuclear SREBP-2. 22:6,n-3 transiently inhibits insulin-induced Akt phosphorylation but induces Erk phosphorylation. Inhibitors of Erk phosphorylation, but not overexpressed constitutively active Akt, rapidly attenuate 22:6,n-3 suppression of nSREBP-1. Thus, 22:6,n-3 suppresses hepatocyte nSREBP-1 through 26S proteasome- and Erk-dependent pathways. These studies reveal a novel mechanism for n-3 PUFA regulation of hepatocyte nSREBP-1 and lipid metabolism.
...
PMID:Docosahexaneoic acid (22:6,n-3) regulates rat hepatocyte SREBP-1 nuclear abundance by Erk- and 26S proteasome-dependent pathways. 1622 32

The structure-activity relationship of Rho kinase inhibitors bearing an isoquinoline scaffold was studied. N-(1-Benzyl-3-pyrrolidyl)-N-(5-isoquinolyl)amine analogues were optimized with respect to their inhibitory potencies for the enzyme and for chemotaxis. The potent analogues were further evaluated by an ex vivo test in which the selected compounds were orally administered to rats, and the Rho kinase inhibitory potency observed in the rat serum was evaluated 3h after the administration. Compound 23g showed a high level of Rho kinase inhibitory activity in the rat serum and was stable in an in vitro metabolic test using a microsomal cytochrome preparation. The (R)-isomer of 23g displayed a higher level of inhibitory potency than the (S)-isomer in a cell-free kinase assay and in the cell migration assay (IC(50)(ENZ)=25 nM and IC(50)(MCP)=1 microM). The (R)-isomer successfully inhibited the phosphorylation of MBS (myosin-binding subunit) in cells.
...
PMID:Design and synthesis of rho kinase inhibitors (III). 1708 87

Proteasome activity takes place in the cytosolic compartment and acts to degrade several proteins translated and unfolded. In transfected CHO cells expressing thyroid peroxidase (TPO), just-translated TPO undergoes proteasome activity, and then a second proteolytic system degrades more mature forms of TPO. A plasminogen-like (Pl-like) protease is found in microsomal liver membranes and in the thyroid. In the thyroid, this Pl-like protease is localized in the follicular lumen and efficiently degrades thyroglobulin (Tg) in vitro. Here we checked for the presence, in purified endoplasmic reticulum (ER) membranes of transfected CHO and in rough microsomes purified from thyroid tissue, of a second proteolytic system, different from the proteasome, and active against the two major proteins of the thyroid gland, TPO and Tg. We first confirmed that this proteolytic system was able to degrade folded endogenous TPO. We showed also that externally added TPO (folded form) was degraded by opened vesicles of ER in the same system. For thyroid tissue, we showed that added TPO, as well as purified Tg, was degraded by some unknown membrane-associated protease(s) in human and porcine thyroid rough microsomes, whereas BSA and IgG were not. These results indicated that major thyroid glycoproteins are preferential substrates of such protease(s). Immunoblot and zymography experiments identified the unknown membrane-associated protease in rough microsomes from thyroid tissues as being a Pl-like protease. These results highly suggest that this system acts as a nonproteasomal degradation enzyme at the ER level, and we hypothesize that it contributes in regulating the level of major thyroid glycoproteins.
...
PMID:A plasminogen-like protease in thyroid rough microsomes degrades thyroperoxidase and thyroglobulin. 1733 62

Alzheimer disease-associated beta-amyloid peptide is generated from its precursor protein APP. By using the yeast two-hybrid assay, here we identified HtrA2/Omi, a stress-responsive chaperone-protease as a protein binding to the N-terminal cysteinerich region of APP. HtrA2 coimmunoprecipitates exclusively with immature APP from cell lysates as well as mouse brain extracts and degrades APP in vitro. A subpopulation of HtrA2 localizes to the cytosolic side of the endoplasmic reticulum (ER) membrane where it contributes to ER-associated degradation of APP together with the proteasome. Inhibition of the proteasome results in accumulation of retrotranslocated forms of APP and increased association of APP with HtrA2 and Derlin-1 in microsomal membranes. In cells lacking HtrA2, APP holoprotein is stabilized and accumulates in the early secretory pathway correlating with elevated levels of APP C-terminal fragments and increased Abeta secretion. Inhibition of ER-associated degradation (either HtrA2 or proteasome) promotes binding of APP to the COPII protein Sec23 suggesting enhanced trafficking of APP out of the ER. Based on these results we suggest a novel function for HtrA2 as a regulator of APP metabolism through ER-associated degradation.
...
PMID:HtrA2 regulates beta-amyloid precursor protein (APP) metabolism through endoplasmic reticulum-associated degradation. 1768 15

De novo autoimmune hepatitis (AIH) occurs after liver transplantation for nonautoimmune disorders. Autoantibodies so-called atypical anti-liver/kidney microsome antibodies (LKMA) with an unusual liver/kidney cytoplasmic staining as judged by indirect immunofluorescence, can be detected in some patients' sera. Few studies investigated their molecular targets, and the aim of this work was to identify the atypical anti-LKMA targets by proteomic tool. This proteomic approach consisted of (a) two-dimensional gel electrophoresis of cytosolic and microsomal proteins obtained by differential centrifugations of rat liver and rat kidney, followed by (b) two-dimensional immunoblotting with sera of patients with de novo AIH (n = 8, including 2 with anti-LKMA antibodies) and then (c) identifications of interest spots performed by ion trap mass spectrometry. By this way several proteins at 25 kDa were unambiguously identified: isoforms of carbonic anhydrase III, members of different glutathione S-transferase (GST) families, and subunit beta1 of proteasome. This is the first report of proteasome and carbonic anhydrase III as autoantigens in de novo AIH. These results could lead to a better diagnosis of this disease using identified autoantigens in diagnostic tests, and strengthen proteomic approach as a new way of autoantigens investigation.
...
PMID:Identification by proteomic tool of atypical anti-liver/kidney microsome autoantibodies targets in de novo autoimmune hepatitis after liver transplantation. 1778 24

Misfolded proteins in the endoplasmic reticulum (ER) are eliminated by a process known as ER-associated degradation (ERAD), which starts with misfolded protein recognition, followed by ubiquitination, retrotranslocation to the cytosol, deglycosylation, and targeting to the proteasome for degradation. Actions of multisubunit protein machineries in the ER membrane integrate these steps. We hypothesized that regulation of the multisubunit machinery assembly is a mechanism by which ERAD activity is regulated. To test this hypothesis, we investigated the potential regulatory role of the small p97/VCP-interacting protein (SVIP) on the formation of the ERAD machinery that includes ubiquitin ligase gp78, AAA ATPase p97/VCP, and the putative channel Derlin1. We found that SVIP is anchored to microsomal membrane via myristoylation and co-fractionated with gp78, Derlin1, p97/VCP, and calnexin to the ER. Like gp78, SVIP also physically interacts with p97/VCP and Derlin1. Overexpression of SVIP blocks unassembled CD3delta from association with gp78 and p97/VCP, which is accompanied by decreases in CD3delta ubiquitination and degradation. Silencing SVIP expression markedly enhances the formation of gp78-p97/VCP-Derlin1 complex, which correlates with increased degradation of CD3delta and misfolded Z variant of alpha-1-antitrypsin, established substrates of gp78. These results suggest that SVIP is an endogenous inhibitor of ERAD that acts through regulating the assembly of the gp78-p97/VCP-Derlin1 complex.
...
PMID:Identification of SVIP as an endogenous inhibitor of endoplasmic reticulum-associated degradation. 1787 46

Intracellular infectious hepatitis C virus (HCV) particles display a distinctly higher buoyant density than do secreted virus particles, suggesting that the characteristic low density of extracellular HCV particles is acquired during viral egress. We took advantage of this difference to examine the determinants of assembly, maturation, degradation, and egress of infectious HCV particles. The results demonstrate that HCV assembly and maturation occur in the endoplasmic reticulum (ER) and post-ER compartments, respectively, and that both depend on microsomal transfer protein and apolipoprotein B, in a manner that parallels the formation of very-low-density lipoproteins (VLDL). In addition, they illustrate that only low-density particles are efficiently secreted and that immature particles are actively degraded, in a proteasome-independent manner, in a post-ER compartment of the cell. These results suggest that by coopting the VLDL assembly, maturation, degradation, and secretory machinery of the cell, HCV acquires its hepatocyte tropism and, by mimicry, its tendency to persist.
...
PMID:Cellular determinants of hepatitis C virus assembly, maturation, degradation, and secretion. 1807 7


<< Previous 1 2 3 4 5 6 Next >>

---