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)

A multicatalytic proteinase (MCP) purified from lobster claw and abdominal muscles degrades a variety of peptide and protein substrates. The enzyme is activated by low concentrations (0.03%) of sodium dodecyl sulfate (SDS) and brief (1 min) heating at 60 degrees C. The lobster MCP can assume three stable and functionally distinct states in vitro; these are classified as the basal, heat-activated, and SDS-activated forms. The basal MCP possessed high trypsin-like peptidase activity and low chymotrypsin-like peptidase, peptidylglutamyl-peptide hydrolase, and caseinolytic activities; incubation of the basal form with SDS stimulated the peptidylglutamyl-hydrolase activity about 30-fold and inhibited the other three activities 80% to 100%. Heating the basal form stimulated caseinolytic activity about 6-fold with little effect on the peptidase activities. The heat-activated enzyme also degraded myosin, tropomyosin, troponin, and actin depolymerizing factor; alpha-actinin was resistant to proteolysis. Incubation of the heat-activated MCP with SDS inhibited the trypsin-like, chymotrypsin-like, and proteinase activities 95 to 100% and stimulated the peptidylglutamyl-hydrolase activity about 16-fold. Incubation of myosin with either the basal or the heat-activated forms in the presence of SDS generated identical proteolytic fragments of the myosin heavy chain, suggesting that SDS induced a third form that can be produced from either the basal or the heat-activated forms. The heat-activated form produced proteolytic fragments of myosin heavy chain different from those generated by either basal or heat-activated enzymes in the presence of SDS. Furthermore, 100 mM KCl stimulated the caseinolytic activity of the heat-activated form 24% and inhibited the trypsin-like and peptidylglutamyl-hydrolase activities 56 and 20%, respectively. These results, though indirect, suggest that heating induced a proteinase activity that was distinct from the three peptidase activities. Activation of the basal form with SDS was reversible, since precipitation of dodecyl sulfate with 100 mM KCl restored trypsin-like activity and inhibited peptidylglutamyl-hydrolase activity. In contrast, removal of dodecyl sulfate from the SDS-activated form that was derived from the heat-activated MCP induced its conversion to the basal form. Thus, although heat-activation was irreversible, the heat-activated form was converted back to the basal form via the SDS-activated form.
...
PMID:Sodium dodecyl sulfate and heat induce two distinct forms of lobster muscle multicatalytic proteinase: the heat-activated form degrades myofibrillar proteins. 189 47

In this review, our current knowledge on the structural proteins of vertebrate skeletal muscle is briefly outlined. Structural proteins include the contractile proteins (actin and myosin), the major regulatory proteins (troponin and tropomyosin), the minor regulatory proteins (M-protein, C-protein, F-protein, I-protein, and actinins), and the scaffold proteins (connectin, desmin, and Z-protein). In addition, the relative turnover rates of the muscle proteins (M-protein greater than or equal to troponin greater than soluble protein as a whole greater than tropomyosin not equal to alpha-actinin greater than myosin greater than 10S-actinin greater than actin) are discussed. The changes in the turnover of muscle proteins are compared in denervated and dystrophic muscles. The properties of the various proteases in muscle, including alkaline protease, calcium-activated neutral protease (CANP), and acidic protease (cathepsins), and the structural alterations of myofibrils by these proteases are also described. Finally, the role of proteases and their inhibitors in diseased muscle is summarized, with focus on CANP and its inhibitors, leupeptin and E-64.
...
PMID:Dynamic aspects of structural proteins in vertebrate skeletal muscle. 703 67

The physiologic function of proteasome remains unclear. Evidence suggests a role in degradation of ubiquitin-protein conjugates, MHC antigen presentation, and some specificity of substrate within certain cell types. To explore further the properties of proteasome we have examined its effect on a well defined structure, the myofibril. We find that despite its large size (20S) proteasome is able to degrade myofibrils and intact, permeabilized muscle fibrils. The proteins degraded showed some specificity because actin, myosin and desmin were degraded faster than alpha-actinin, troponin T and tropomyosin. Changes in ultrastructure were slow and included a general loss of structure with Z and I bands effected before the M band and costameres.
...
PMID:Proteolytic activity of proteasome on myofibrillar structures. 756 68

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

The goal of this research was to evaluate the roles of calpains and their interactions with the proteasome and the lysosome in degradation of individual sarcomeric and cytoskeletal proteins in cultured muscle cells. Rat L8-CID muscle cells, in which we expressed a transgene calpain inhibitor (CID), were used in the study. L8-CID cells were grown as myotubes after which the relative roles of calpain, proteasome and lysosome in total protein degradation were assessed during a period of serum withdrawal. Following this, the roles of proteases in degrading cytoskeletal proteins (desmin, dystrophin and filamin) and of sarcomeric proteins (alpha-actinin and tropomyosin) were assessed. Total protein degradation was assessed by release of radioactive tyrosine from pre-labeled myotubes in the presence and absence of protease inhibitors. Effects of protease inhibitors on concentrations of individual sarcomeric and cytoskeletal proteins were assessed by Western blotting. Inhibition of calpains, proteasome and lysosome caused 20, 62 and 40% reductions in total protein degradation (P<0.05), respectively. Therefore, these three systems account for the bulk of degradation in cultured muscle cells. Two cytoskeletal proteins were highly-sensitive to inhibition of their degradation. Specifically, desmin and dystrophin concentrations increased markedly when calpain, proteasome and lysosome activities were inhibited. Conversely, sarcomeric proteins (alpha-actinin and tropomyosin) and filamin were relatively insensitive to the addition of protease inhibitors to culture media. These data demonstrate that proteolytic systems work in tandem to degrade cytoskeletal and sarcomeric protein complexes and that the cytoskeleton is more sensitive to inhibition of degradation than the sarcomere. Mechanisms, which bring about changes in the activities of the proteases, which mediate muscle protein degradation are not known and represent the next frontier of understanding needed in muscle wasting diseases and in muscle growth biology.
...
PMID:Degradation of sarcomeric and cytoskeletal proteins in cultured skeletal muscle cells. 1460 48

We have undertaken to continue the proteomic study of human umbilical vein endothelial cells (HUVECs) using the combination of 2-DE, automated trypsin digestion, and PMF analysis after MALDI-TOF MS and peptide sequencing using nano LC-ESI-MS/MS. The overall functional characterization of the 162 identified proteins from primary cultures of HUVECs confirms the metabolic capabilities of endothelium and illustrates various cellular functions more related to cell motility and angiogenesis, protein folding, anti-oxidant defenses, signal transduction, proteasome pathway and resistance to apoptosis. In comparison with controls cells, the differential proteomic analysis of HUVECs treated by the pro-apoptotic topoisomerase inhibitor etoposide further revealed the variation of eight proteins, namely, GRP78, GRP94, valosin-containing protein, proteinase inhibitor 9, cofilin, 37-kDa laminin receptor protein, bovine apolipoprotein, and tropomyosin. These data suggest that etoposide-induced apoptosis of human vascular endothelial cells results from the intricate involvement of multiple apoptosis processes including at least the mitochondrial and the ER stress pathways. The presented 2-D pattern and protein database, as well as the data related to apoptosis of HUVECs, are available at http://www.huvec.com.
...
PMID:Proteomics of human umbilical vein endothelial cells applied to etoposide-induced apoptosis. 1613 Jan 69

Muscle wasting in chronic kidney disease (CKD) and other catabolic diseases (e.g. sepsis, diabetes, cancer) can occur despite adequate nutritional intake. It is now known that complications of these various disorders, including acidosis, insulin resistance, inflammation, and increased glucocorticoid and angiotensin II production, all activate the ubiquitin-proteasome system (UPS) to degrade muscle proteins. The initial step in this process is activation of caspase-3 to cleave the myofibril into its components (actin, myosin, troponin, and tropomyosin). Caspase-3 is required because the UPS minimally degrades the myofibril but rapidly degrades its component proteins. Caspase-3 activity is easily detected because it leaves a characteristic 14kD actin fragment in muscle samples. Preliminary evidence from several experimental models of catabolic diseases, as well as from studies in patients, indicates that this fragment could be a useful biomarker because it correlates well with the degree of muscle degradation in dialysis patients and in other catabolic conditions.
...
PMID:Muscle wasting in chronic kidney disease: the role of the ubiquitin proteasome system and its clinical impact. 1798 22

Atrazine (ATRA) is the most commonly applied herbicide in the United States and is frequently detected in drinking water at significant levels. After oral exposure, ATRA metabolism yields diaminochlorotriazine (DACT), an electrophilic molecule that has been shown to form covalent protein adducts. This research was designed to identify ATRA-induced protein adducts formed in the pituitary gland of ATRA-exposed rats and in DACT-exposed LbetaT2 rat pituitary cells. Immunohistochemistry showed diffuse cytoplasmic and nuclear staining in both pituitary sections and LbetaT2 cells indicating the formation of DACT protein adducts. Protein targets from both rat pituitaries and LbetaT2 cell culture were identified following two-dimensional electrophoresis (2DE), immunodetection, and matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis. Western blots from both exposed rats and LbetaT2 cells revealed over 30 DACT-modified spots that were not present in control animals. Protein spots were matched to concurrently run 2DE gels stained with Sypro Ruby, excised, and in-gel-digested with trypsin. Mass spectrometry analysis of digest peptides resulted in the identification of 19 spots and 8 unique proteins in the rats and 21 spots and 19 unique proteins in LbetaT2 cells. The identified proteins present in both sample types included proteasome activator complex subunit 1, ubiquitin carboxyl-terminal hydrolase isozyme L1, tropomyosin, ERp57, and RNA-binding proteins. Each of these proteins contains active-site or solvent-exposed cysteine residues, making them viable targets for covalent modification by DACT.
...
PMID:Proteomic analysis of diaminochlorotriazine adducts in wistar rat pituitary glands and LbetaT2 rat pituitary cells. 1837 Apr 13

Gaps in our knowledge exist regarding the degradation of the tropomyosin-regulated kinase A (TrkA) receptor after addition of neurotrophin, nerve growth factor (NGF). TrkA is rapidly and transiently ubiquitinated upon addition of NGF. Here, we demonstrate that the polyubiquitin tag plays a definitive role in receptor sorting. Treatment of PC12 cells with lactacystin prevented NGF-dependent deubiquitination and degradation of TrkA. However, treatment with methylamine, bafilomycin or leupeptin, did not prevent NGF-dependent deubiquitination but blocked the degradation of TrkA. Employing co-immunoprecipitation, biochemical fractionation and confocal microscopy, the kinetics of receptor trafficking post-internalization was observed to occur as a sequel from endosome/multivesicular body, proteasomes, culminating with degradation in the lysosomes. The trafficking of the polyubiquitin-deficient TrkA receptor mutant K485R was impaired and likewise failed to degrade revealing that the receptor escapes degradation. The interaction of TrkA with proteasomes was confirmed by purification and co-immunoprecipitation. We provide evidence that proteasomal deubiquitinating enzymes trim K63-ubiquitin chains from the TrkA receptor prior to its delivery to lysosomes for degradation. Taken together, our results reveal the existence of a novel proteasome-dependent step in receptor degradation.
...
PMID:TrkA receptor endolysosomal degradation is both ubiquitin and proteasome dependent. 1841 53

The ability of synapses to undergo changes in structure and function in response to alterations of neuronal activity is an essential property of neural circuits. One way that this is achieved is through global changes in the molecular composition of the synapse; however, it is not clear how these changes are coupled to the dynamics of neuronal activity. Here we found that, in cultured rat cortical neurons, bidirectional changes of neuronal activity led to corresponding alterations in the expression of brain-derived neurotrophic factor (BDNF) and phosphorylation of its receptor tropomyosin-related kinase B (TrkB), as well as in the level of synaptic proteins. Exogenous BDNF reversed changes in synaptic proteins induced by chronic activity blockade, while inhibiting Trk kinase activity or depleting endogenous BDNF abolished the concentration changes induced by chronic activity elevation. Both tetrodotoxin and bicuculline had significant, but opposite, effects on synaptic protein ubiquitination in a time-dependent manner. Furthermore, exogenous BDNF was sufficient to increase ubiquitination of synaptic proteins, whereas scavenging endogenous BDNF or inhibiting Trk kinase activity prevented the ubiquitination of synaptic proteins induced by chronic elevation of neuronal activity. Inhibiting the proteasome or blocking protein polyubiquitination mimicked the effect of tetrodotoxin on the levels of synaptic proteins and canceled the effects of BDNF. Our study indicates that BDNF-TrkB signaling acts upstream of the ubiquitin proteasome system, linking neuronal activity to protein turnover at the synapse.
...
PMID:Brain-derived neurotrophic factor-tropomyosin-related kinase B signaling contributes to activity-dependent changes in synaptic proteins. 1847 5


1 2 Next >>

---