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

There is substantial evidence that cytokines induce apoptosis of vascular smooth muscle cells (VSMCs) in atherosclerosis. Its regulation, however, is not completely defined. The aim of this study is to investigate whether proteasome activity is related with apoptosis in VSMCs by tumor necrosis factor-alpha (TNF-alpha). Rat aorta smooth muscle cells were treated with TNF-alpha and proteasome inhibitor MG132 and then cell death was determined by morphology, viability, and DNA fragmentation. MG132 or TNF-alpha alone did not induce cell death. In contrast, co-treatment of TNF-alpha and proteasome inhibitor induced death and DNA degradation in VSMCs, suggesting proteasome inhibitor enhanced death activity of TNF-alpha. The death was not blocked by ascorbic acid but by nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine. Both caspase-3 and -8 were activated during the death by the proteasome inhibitor and TNF-alpha. The death was effectively blocked by the caspase-3 inhibitor z-DEVD-fmk, suggesting a role of caspase-3 in the death. Nonetheless, there were no significant alterations in the level of Bcl-2, Bcl-X(L), Bax and Bak by the proteasome inhibitor, nor any evidence of cytochrome (cyt) c release into cytosol from dying cells, suggesting that cyt c is not involved. These results suggest that proteasome inhibition potentiates TNF-mediated death in VSMCs in a cyt c-independent pathway. The present study proposes a new mechanism by which VSMCs undergo death by cytokines.
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PMID:Enhancement of TNF-alpha-mediated cell death in vascular smooth muscle cells through cytochrome c-independent pathway by the proteasome inhibitor. 1256 Jan 2

MafBx and Murf are two new rat E3 ubiquitin ligases induced in muscle atrophy. Our goal was to investigate whether lipopolysaccharide (LPS) injection, a model of muscle catabolism, is associated with increased expression of MafBx and Murf. LPS (750 microg/100 g body weight) induces MafBx and Murf mRNA (respectively, 23-fold and 33-fold after 12 h; P<0.001). A transient induction of tumor necrosis factor-alpha mRNA (21-fold; P<0.001 at 3 h) and a decrease of insulin like growth factor-I mRNA (50%; P<0.001 at 6 h), two potential regulators of the ubiquitin-proteasome system were also demonstrated. In summary, MafBx and Murf mRNA are up-regulated in response to LPS and might play a role in the muscle proteolysis observed.
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PMID:Induction of MafBx and Murf ubiquitin ligase mRNAs in rat skeletal muscle after LPS injection. 1278 19

Lymphocyte development, selection, and education are strictly controlled to prevent autoimmunity, with potentially autoreactive cells being removed by apoptosis. Dysregulation of apoptosis is a central defect in diverse murine autoimmune diseases. In murine models of autoimmune lupus, for example, mutations in the death receptor Fas (CD95) or in its ligand, FasL (CD95L), have been identified and shown to render lymphoid cells resistant to apoptosis. In contrast, select lymphoid subpopulations of mice with autoimmune diabetes manifest an increased susceptibility to apoptosis as a result of impaired activation of the transcription factor nuclear factor-kappa B (NF-kappaB), which normally protects cells against tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis. The genetic basis of this defect in NF-kappaB activation is a mutation in the promoter-enhancer region of a gene that encodes an essential subunit (LMP2) of the proteasome. Although no specific genetic defects have been identified in most common forms of human autoimmune disease, functional assays consistently demonstrate heightened apoptosis attributable to multiple death signaling pathways.
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PMID:Role of defective apoptosis in type 1 diabetes and other autoimmune diseases. 1279 17

Following binding its death receptor on the plasma membrane, tumor necrosis factor (TNF) induces the receptor trimerization and recruits a number of death domain-containing molecules to form the receptor complex. The complex promotes activation of downstream caspase cascade and induces degradation of IkappaBalpha. Caspases are activated using mechanisms of oligomeration and 'self-controlled proteolysis'. According to their structures and functions, apoptosis related caspases can be divided into upstream and downstream caspases. In general, upstream caspases cleave and activate downstream caspases by proteolysis of the Asp-X site. Activated caspases then cleaved target substrates. To date, more than 70 proteins have been identified to be substrates of caspases in mammalian cells. Caspases can alter the function of their target proteins by destroying structural components of the cytoskeleton and nuclear scaffold or by removing their regulatory domains. Activation of NF-kappaB is dependent on the degradation of IkappaBalpha. IkappaB kinase (IKK) phosphorylates IkappaBalpha at the residues 32 and 36 followed by polyubiquitination at lysine 21 and 22 and subsequent degradation of the molecules by 26S proteasome. There is extensive crosstalk between the apoptotic and NF-kappaB signaling pathways that emanate from TNF-R1. On the one hand, activation of NF-kappaB can inactivate caspases; on the other hand, activated caspases can inhibit the activation of NF-kappaB. Both processes involve in proteolysis. This crosstalk may be important for maintaining the balance between the two pathways and for determining whether a cell should live or die.
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PMID:Proteolytic signaling by TNFalpha: caspase activation and IkappaB degradation. 1282 2

The human immunodeficiency virus type 1 Vpu protein acts as an adaptor for the proteasomal degradation of CD4 by recruiting CD4 and beta-transducin repeat-containing protein (betaTrCP), the receptor component of the multisubunit SCF-betaTrCP E3 ubiquitin ligase complex. We showed that the expression of a Vpu-green fluorescent fusion protein prevented the proteosomal degradation of betaTrCP substrates such as beta-catenin, IkappaBalpha, and ATF4, which are normally directly targeted to the proteasome for degradation. Beta-catenin was translocated into the nucleus, whereas the tumor necrosis factor-induced nuclear translocation of NFkappaB was impaired. Beta-catenin was also up-regulated in cells producing Vpu+ human immunodeficiency virus type 1 but not in cells producing Vpu-deficient viruses. The overexpression of ATF4 also provoked accumulation of beta-catenin, but to a lower level than that resulting from the expression of Vpu. Finally, the expression of Vpu induces the exclusion of betaTrCP from the nucleus. These data suggest that Vpu is a strong competitive inhibitor of betaTrCP that impairs the degradation of SCFbetaTrCP substrates as long as Vpu has an intact phosphorylation motif and can bind to betaTrCP.
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PMID:HIV-1 Vpu sequesters beta-transducin repeat-containing protein (betaTrCP) in the cytoplasm and provokes the accumulation of beta-catenin and other SCFbetaTrCP substrates. 1456 67

Apo2L/TRAIL (tumor necrosis factor-related apoptosis inducing ligand (TRAIL), also known as Apo2L) is a potentially important anticancer agent awaiting clinical trials. Unfortunately, however, some cancer cells exhibit resistance to Apo2L/TRAIL, which could limit the use of this potentially promising anticancer agent. Although the molecular basis of the inherent or acquired resistance to Apo2L/TRAIL remains unclear, previous studies indicate that Bax deficiency can confer resistance to Apo2L/TRAIL. Proteasome inhibition is also emerging as a promising therapeutic strategy to manage human malignancies. Here, we report that proteasome inhibitor MG132 upregulates Apo2L/TRAIL death receptor 5 expression in both Bax-proficient and -deficient HCT116 cells. MG132 effectively cooperated with Apo2L/TRAIL to induce apoptosis in both Bax-proficient and -deficient cells that was coupled with caspases-8 and -3 activation and Bid cleavage. Although both agents in combination also induced cytochrome c and Smac release from mitochondria into cytosol and activated caspase-9 in Bax-proficient cells, their effects on these events were significantly diminished in Bax-deficient cells. These results suggest that Bax is not absolutely required for death receptor 5-dependent apoptotic signals and MG132 by upregulating DR5 effectively cooperates with Apo2L/TRAIL to overcome Bax deficiency-induced resistance to Apo2L/TRAIL. Our results have important clinical implications in that the use of Apo2L/TRAIL and proteasome inhibitors in combination could prove to be a novel therapeutic strategy to manage the Apo2L/TRAIL-resistant tumors.
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PMID:Proteasome inhibitor MG132 upregulates death receptor 5 and cooperates with Apo2L/TRAIL to induce apoptosis in Bax-proficient and -deficient cells. 1469 51

Small volumes of cervical secretions have limited measurements of immunity at the cervix, which may be important to studies of human papillomavirus (HPV). We report the use of recycling immunoaffinity chromatography to efficiently study immune profiles in cervical secretions. Frozen pairs of plasma and cervical secretions (collected on ophthalmic sponges) were selected randomly from women with normal cervical cytology (n = 50) participating in a natural history study of HPV in Guanacaste, Costa Rica. Single 25- micro l aliquots of plasma and (diluted) cervical secretions were assayed for interleukin (IL) -1 beta, -2, -4, -6, -8, -10, -12, -13, -15, IFN-alpha, -beta, -gamma, tumor necrosis factor-alpha, -beta, RANTES (regulated on activation normal T-cell express and secreted), MCP-1 (monocyte chemoattractant protein), -2, -3, macrophage inflammatory protein-1 alpha, -1 beta (regulated on activation normal T-cell express and secreted), macrophage colony-stimulating factor, IgG, IgA, and cyclooxygenase 2. All of the specimens were tested as blind replicates, and refrozen plasma was retested 4 months later. To evaluate the reproducibility of the repeat measurements and to examine the correlation between plasma and cervical secretions, we calculated kappa values with 95% confidence intervals among categorized analyte values and Spearman correlation coefficients (rho) among detectable, continuous analyte values. Measurements of all of the analytes in either plasma or cervical secretions were highly reproducible, with all of the kappa > or = 0.78 (70% above 0.90), and all of the rho > or = 0.88 (96% above 0.90). Only IL-1 beta (kappa = 0.60 and rho = 0.82) and IL-6 (kappa = 0.50 and rho = 0.78) levels were strongly correlated between plasma and cervical secretions. IFN-gamma, tumor necrosis factor-beta, RANTES, MCP-1, MCP -2, macrophage inflammatory protein-1 alpha, and macrophage colony-stimulating factor levels were especially poorly correlated between plasma and cervical secretions (kappa < or = 0.25 and rho < or = 0.25). We conclude that recycling immunoaffinity chromatography is a reproducible method of measuring immune profiles from biological specimens, and immune profiles are not well correlated between plasma and cervical secretions, perhaps necessitating cervical collections to study cervix-specific immunity in HPV natural history studies.
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PMID:Immune profiling of plasma and cervical secretions using recycling immunoaffinity chromatography. 1469 36

Tissue factor (TF) is expressed rapidly by human monocytes exposed to a variety of agonists such as lipopolysaccharide (LPS) or tumor necrosis factor-alpha. Activation of both activator protein-1 (AP-1; c-Jun/c-Fos) and nuclear factor-kappaB (NF-kappaB) pathways is necessary for maximal induction of the TF gene. It has been demonstrated that activation of both AP-1 and NF-kappaB is correlated with the degradation of both phosphorylated c-Jun and inhibitor kappaB (IkappaB) by proteasome. The present study was designed to investigate whether various protease inhibitors, including proteasome inhibitors, affect TF expression in monocytic cells. Protease inhibitors, 3,4-dichloroisocoumarin (DCI), N-tosyl-l-phenylalanine chloromethyl ketone (TPCK), and N-acetyl-Leu-Leu-norleucinal (ALLN) induced TF activity in monocytic cells in a dose- and time-dependent manner at the level of the transcription of the TF gene, which was mediated through inducing phosphorylation of both Jun-N-terminal kinase and p38. The early growth response-1 (Egr-1) pathway was not affected. The NF-kappaB pathway was not activated; rather it was inhibited. These results were distinct from the findings previously reported for LPS-stimulated cells. The present study demonstrated that some protease inhibitors might act as stress and induced TF expression with direct phosphorylation of JNK and p38, followed by phosphorylation and activation of AP-1 in monocytic cells. This evidence may help elucidate further regulatory mechanisms of TF induction, and might have physiological significance for the clinically challenged use of proteasome inhibitors. In addition to phosphorylation of JNK and p38, an unknown signal pathway needs to be clarified for TF induction.
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PMID:Induction of tissue factor expression in human monocytic cells by protease inhibitors through activating activator protein-1 (AP-1) with phosphorylation of Jun-N-terminal kinase and p38. 1504 Dec 76

The processing of the nfkappab2 gene product p100 to generate p52 is a regulated event, which is important for the instrumental function of NF-kappaB. We previously demonstrated that this tightly controlled event is regulated positively by NF-kappaB-inducing kinase (NIK) and its downstream kinase, IkappaB kinase alpha (IKKalpha). However, the precise mechanisms by which NIK and IKKalpha induce p100 processing remain unclear. Here, we show that, besides activating IKKalpha, NIK also serves as a docking molecule recruiting IKKalpha to p100. This novel function of NIK requires two specific amino acid residues, serine 866 and serine 870, of p100 that are known to be essential for inducible processing of p100. We also show that, after being recruited into p100 complex, activated IKKalpha phosphorylates specific serines located in both N- and C-terminal regions of p100 (serines 99, 108, 115, 123, and 872). The phosphorylation of these specific serines is the prerequisite for ubiquitination and subsequent processing of p100 mediated by the beta-TrCP ubiquitin ligase and 26 S proteasome, respectively. These results highlight the critical but different roles of NIK and IKKalpha in regulating p100 processing and shed light on the mechanisms mediating the tight control of p100 processing. These data also provide the first evidence for explaining why overexpression of IKKalpha or its activation by many other stimuli such as tumor necrosis factor and mitogens fails to induce p100 processing.
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PMID:Induction of p100 processing by NF-kappaB-inducing kinase involves docking IkappaB kinase alpha (IKKalpha) to p100 and IKKalpha-mediated phosphorylation. 1514 Aug 82

The 14-3-3sigma is a negative regulator of the cell cycle, which is induced by p53 in response to DNA damage. It has been characterized as an epithelium-specific marker and down-regulation of the protein has been shown in breast cancers, suggesting its tumor-suppressive activity in epithelial cells. Here we demonstrate that 14-3-3sigma protein is down-regulated in human prostate cancer cell lines, LNCaP, PC3, and DU145 compared with normal prostate epithelial cells. Immunohistochemical analysis of primary prostate cells shows that the expression of 14-3-3sigma protein is epithelial cell-specific. Among prostate pathological specimens, > 95% of benign hyperplasia samples show significant and diffuse immunostaining of 14-3-3sigma in the cytoplasm whereas < 20% of carcinoma samples show positive staining. In terms of mechanisms for the down-regulation of 14-3-3sigma in prostate cancer cells, hypermethylation of the gene promoter plays a causal role in LNCaP cells as 14-3-3sigma mRNA level was elevated by 5-aza-2'-deoxycytidine demethylating treatment. Intriguingly, the proteasome-mediated proteolysis is responsible for 14-3-3sigma reduction in DU145 and PC3 cells, as 14-3-3sigma protein expression was increased by treatment with a proteasome inhibitor MG132. Furthermore, tumor necrosis factor-related apoptosis-inducing ligand enhances 14-3-3sigma gene and protein expression in DU145 and PC3 cells. These data suggest that 14-3-3sigma expression is down-regulated during the neoplastic transition of prostate epithelial cells.
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PMID:14-3-3sigma is down-regulated in human prostate cancer. 1518 53


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