UNIPROT:P08758 - FACTA Search

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Query: UNIPROT:P08758 (annexin V)
9,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have studied the subcellular localization and expression levels of proteasomes during apoptosis in a lung cancer cell line. Apoptosis was induced by exposing the cells to 200 microM olomoucine, a specific cyclin-dependent kinase inhibitor. The morphological changes characteristic for apoptotic cells were visible: the cells reduced in size, the chromatin condensed and the membranes became convoluted. As the process continued, the nuclei became fragmented, and the cells broke up into cytoplasmic vesicles and apoptotic bodies. Immunocytochemically, apoptotic cells were detected by the ability to bind annexin V at their surface. During the initial stages of apoptosis, proteasomes were present in the nucleus as well as in the cytoplasm. Upon increased chromatin condensation, nuclear proteasomes were found predominantly surrounding the chromatin, while the chromatin itself remained devoid of staining. That the proteasomes persisted relatively long in the apoptotic cells was shown by immunoblotting of non-denaturing gels, which indicated that both 20S and 26S proteasomes were present in apoptotic cells. In immunofluoresence microscopy the proteasome fluorescence intensity of apoptotic cells seemed higher than that of non-apoptotic cells. These differences in intensity were even more pronounced after Triton X-100 extraction. Flow cytometry revealed that the absolute levels of proteasome staining in cells were decreased after Triton X-100 extraction. However, no differences in staining levels were detected between apoptotic and non-apoptotic cells. A relative increase of proteasome concentration through cell shrinkage or a concentration in certain cell compartments may be the origin of the apparently increased signal that was seen in immunofluorescence microscopy. Furthermore, proteasomes were clearly detectable in the apoptotic bodies and cytoplasmic vesicles at the time immunocytochemical reactivity for cytokeratins and lamins had diminished to a large extent. Immunoblotting of denaturing polyacrylamide gels confirmed the results obtained by flow cytometry. The proteasome content was retained only partially in the cells after Triton X-100 extraction, while the intermediate filaments were not detectable anymore in the apoptotic cells.
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PMID:Subcellular localization of proteasomes in apoptotic lung tumor cells and persistence as compared to intermediate filaments. 883 9

Nuclear factor-kappaB (NF-kappaB) regulates the transcription of a variety of genes involved in immune responses, cell growth, and cell death. However, the role of NF-kappaB in muscle biology is poorly understood. We recently reported that tumor necrosis factor-alpha (TNF-alpha) rapidly activates NF-kappaB in differentiated skeletal muscle myotubes and that TNF-alpha acts directly on the muscle cell to induce protein degradation. In the present study, we ask whether NF-kappaB mediates the protein loss induced by TNF-alpha. We addressed this problem by creating stable, transdominant negative muscle cell lines. C2C12 myoblasts were transfected with viral plasmid constructs that induce overexpression of mutant I-kappaBalpha proteins that are insensitive to degradation via the ubiquitin-proteasome pathway. These mutant proteins selectively inhibit NF-kappaB activation. We found that differentiated myotubes transfected with the empty viral vector (controls) underwent a drop in total protein content and in fast-type myosin heavy-chain content during 72 h of exposure to TNF-alpha. In contrast, total protein and fast-type myosin heavy-chain levels were unaltered by TNF-alpha in the transdominant negative cell lines. TNF-alpha did not induce apoptosis in any cell line, as assessed by DNA ladder and annexin V assays. These data indicate that NF-kappaB is an essential mediator of TNF-alpha-induced catabolism in differentiated muscle cells.
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PMID:NF-kappaB mediates the protein loss induced by TNF-alpha in differentiated skeletal muscle myotubes. 1100 79

Hypertonic loading of proteins into cells has been used to introduce soluble proteins into the major histocompatibility complex class I pathway of antigen presentation followed by cytotoxic T-lymphocyte (CTL) induction. The precise mechanism for this pathway is not completely understood. The antigen is either processed and presented by/on the same cell or by professional antigen-presenting cells (APC) after taking up the antigen from damaged or apoptotic cells. After loading labelled ovalbumin (OVA), it could be co-precipitated with the proteasome complex, supporting the role of this pathway for antigen processing. The processing speed however, appeared to be slow since intact OVA could be detected inside the cells even after 18 hr. This corresponded well with the processing of OVA by isolated proteasomes. On the other hand, enough peptides for recognition of target cells by CTLs were generated in this reaction. One reason for the low level of processing might be that hypertonic loading may damage the cells and inhibit direct processing. In fact, at least 50% of the cells became positive for Annexin V binding after hypertonic loading which indicates severe membrane alterations usually associated with the progress of apoptosis. Annexin V binds to phosphatidylserine residues which also serve as ligand for CD36 expressed on monocytes and some immature dendritic cells. This may direct the phagocytic pathway to hypertonically loaded cells and thus enable professional APCs to present OVA-peptides. Therefore, in addition to the direct processing of OVA, CTLs can be primed by professional APC after uptake of apoptotic, OVA-loaded cells.
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PMID:Mechanism of antigen presentation after hypertonic loading of soluble antigens. 1215 14

Although the participation of the ubiquitin-dependent pathway and of the proteasome in apoptosis has been proposed, its role in this process is not yet clearly defined. In previous studies, we have shown that in the central nervous system of the rat, programmed cell death and the ubiquitin-dependent proteolytic pathway are closely related to each other and that different types of neurons and of glial cells, shown different types of correlation between the two phenomena. In this work, we have used lactacystin, a highly specific inhibitor of the proteasome, to explore in Schwann cell cultures the relationship between the activity of the Ub-dependent pathway and apoptosis. Apoptosis was explored analyzing changes in nuclear morphology, using the Annexin V assay and by flow cytometry. Activity of caspase-3 was also measured. Changes in the levels of ubiquitin-protein conjugates and of the ubiquitin activating enzymes, E1, as well as expression of proteins that instruct the cells to apoptosis (p53, NFkappaB-IkappaB, Bcl2), or that participate in the control and regulation of the cell cycle, were also examined. Our results indicate that the decrease in the activity of the proteasome induced by lactacystin in Schwann cells, induces apoptotic cell death through changes in the concentration of certain key proteins that are involved in the apoptosis-signaling pathways.
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PMID:Apoptosis in Schwann cell cultures is closely interrelated with the activity of the ubiquitin-proteasome proteolytic pathway. 1251 44

Apoptosis, or programmed cell death, is a process where developmental or environmental stimuli activate a genetic program to implement a series of events that culminate in cell death. To study the nature of genes that are induced during the apoptotic death of myeloid precursor cells, representational difference analysis was performed using RNAs derived from 32Dcl3 myeloblastic cells that were proliferating in the presence of IL-3 and cells that were actively undergoing apoptosis as a result of interleukin 3 deprivation for 24 h. This report describes a novel gene [small unstable apoptotic protein (SUAP)] that is up-regulated in these cells after the removal of interleukin 3 and exposure to granulocyte colony stimulating factor. The protein encoded by this gene is a target of the proteasome and does not share homology with other previously characterized proteins. To further define SUAP's role in growth arrest and apoptosis, 32Dcl3 cells that ectopically express SUAP under the control of an inducible promoter were generated and tested for their ability to proliferate under conditions where SUAP expression is induced. These studies show that although the SUAP expressing cells exhibited suppressed proliferation rates, this was not attributable to alterations in cell cycle progression. Rather, SUAP appears to induce the appearance of Annexin V-positive cells, supporting a role for this protein in programmed cell death.
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PMID:Small unstable apoptotic protein, an apoptosis-associated protein, suppresses proliferation of myeloid cells. 1256 17

Recent studies have shown that the transcription factor nuclear factor kappaB (NF-kappaB) regulates critical survival pathways in a variety of cancers, including human T-cell leukemia/lymphotrophic virus 1 (HTLV-1)-transformed CD4 T cells. The activation of NF-kappaB is controlled by proteasome-mediated degradation of the inhibitor of nuclear factor kappaBalpha (IkappaBalpha). We investigated the effects of PS-341, a peptide boronate inhibitor of the proteasome in HTLV-1 Tax transgenic tumors in vitro and in vivo. In Tax transgenic mice, PS-341 administered thrice weekly inhibited tumor-associated NF-kappaB activity. Quantitation of proliferation, apoptosis, and interleukin 6 (IL-6) and IL-10 secretion by tumor cells in culture revealed that the effects of PS-341 on cell growth largely correlated with inhibition of pathways mediated by NF-kappaB. However, the effect of PS-341 on the growth of tumors in Tax transgenic mice revealed heterogeneity in drug responsiveness. The tumor tissues treated with PS-341 show no consistent inhibition of NFkappaB activation in vivo. Annexin V staining indicated that PS-341 response in vivo correlated with sensitivity to apoptosis induced by gamma irradiation. On the other hand, transplanted Tax tumors in Rag-1 mice showed consistent inhibition of tumor growth and prolonged survival in response to the same drug regimen. TUNEL staining indicated that PS-341 treatment sensitizes Tax tumors to DNA fragmentation.
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PMID:Effects of the proteasome inhibitor PS-341 on tumor growth in HTLV-1 Tax transgenic mice and Tax tumor transplants. 1509 Apr 53

The proteasome plays a pivotal role in controlling cell proliferation, apoptosis, and differentiation in a variety of normal and tumor cells. PS-341, a novel boronic acid dipeptide that inhibits 26S proteasome activity, has prominent effects in vitro and in vivo against several solid tumors. We examined its antiproliferation, proapoptotic effects using three human glioblastoma multiforme (GBM) cell lines and five primary GBM explants. PS-341 markedly inhibited proliferation of GBM cell lines and explants in liquid and soft agar culture. These cells developed a G2/M cell cycle arrest with a concomitant decreased percentage of cells in S phase ( approximately 2-fold), associated with an increased expression of p21(WAF1), p27(KIP1), as well as cyclin B1 and decreased levels of CDK2, CDK4, and E2F4. About 35-40% of the cells became apoptotic when exposed to PS-341 (10(-7) M, 24-48 h) as shown by Annexin V analysis; in concert with these findings, immunobloting showed a C-terminal 85 kDa apoptotic fragment of poly ADP-ribose polymerase (PARP), and a decreased level of Bcl2 and Bcl-xl. PS-341 downregulated the expression of Bcl-2 and Bcl-xl in protein levels at an early time of treatment. These changes occurred irrespective of the p53 mutational status of the cells. PS-341 activated JNK/c-Jun signaling in GBM cells, and the JNK inhibitor SP600125 blocked the JNK signaling to reverse partially the PS-341 growth inhibition. PS-341 (10(-7) M, 24 h) decreased nuclear NF-kappaB levels as shown by Western blot, and reduced transcriptional activity of NF-kappaB as measured by reporter assays in these transformed cells. Also, PS-341 enhanced TRAIL (TNF-related apoptosis-inducing ligand) and TNFalpha (tumor necrosis factor alpha) induced cell death and apoptosis (two- to five-fold) in GBM cells. In summary, PS-341 has profound effects on growth and apoptosis of GBM cells, suggesting that PS-341 may be an effective therapy for patients with gliomas.
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PMID:Proteasome inhibitor PS-341 causes cell growth arrest and apoptosis in human glioblastoma multiforme (GBM). 1553 18

Tetrandrine is an antitumor alkaloid isolated from the root of Stephania tetrandra. We find that micromolar concentrations of tetrandrine irreversibly inhibit the proliferation of human colon carcinoma cells in MTT and clonogenic assays by arresting cells in G(1). Tetrandrine induces G(1) arrest before the restriction point in nocodazole- and serum-starved synchronized HT29 cells, without affecting the G(1)-S transition in aphidicolin-synchronized cells. Tetrandrine-induced G(1) arrest is followed by apoptosis as shown by fluorescence-activated cell sorting, terminal deoxynucleotidyl transferase-mediated nick end labeling, and annexin V staining assays. Tetrandrine-induced early G(1) arrest is mediated by at least three different mechanisms. First, tetrandrine inhibits purified cyclin-dependent kinase 2 (CDK2)/cyclin E and CDK4 without affecting significantly CDK2/cyclin A, CDK1/cyclin B, and CDK6. Second, tetrandrine induces the proteasome-dependent degradation of CDK4, CDK6, cyclin D1, and E2F1. Third, tetrandrine increases the expression of p53 and p21(Cip1) in wild-type p53 HCT116 cells. Collectively, these results show that tetrandrine arrests cells in G(1) by convergent mechanisms, including down-regulation of E2F1 and up-regulation of p53/p21(Cip1).
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PMID:Tetrandrine induces early G1 arrest in human colon carcinoma cells by down-regulating the activity and inducing the degradation of G1-S-specific cyclin-dependent kinases and by inducing p53 and p21Cip1. 1560 77

BRICHOS is a domain found in several proteins consisting of approximately 100 amino acids with sequence and structural similarities. Mutations in BRICHOS domain have been associated with both degenerative and proliferative diseases in several nonpulmonary organs, although the pathogenic mechanisms are largely undefined. Recently, several mutations in surfactant protein C (SP-C) mapping to the BRICHOS domain located within the proprotein (proSP-C) have been linked to interstitial lung diseases. In vitro expression of one of these BRICHOS mutants, the exon 4 deletion (hSP-CDeltaexon4), promotes a dominant-negative perinuclear aggregation of the protein. The present study characterizes the trafficking behavior and pathogenic consequences resulting from hSP-CDeltaexon4 expression. Time-lapse and co-localization microscopy studies demonstrated enhanced green fluorescent protein (EGFP)/hSP-CDeltaexon4 expression in calnexin-positive (endoplasmic reticulum [ER]) compartment with subsequent time- and concentration-dependent development of ubiquitinated perinuclear inclusion bodies followed by apoptosis. Compared with controls, EGFP/hSP-CDeltaexon4 promoted upregulation of multiple ER stress species, activated caspase 3, and induced annexin V binding. Furthermore, in GFP-u cells, hSP-CDeltaexon4 directly inhibited proteasome activity. These results support a model whereby proSP-C BRICHOS mutations induce a dynamic toxic gain-of-function, causing apoptotic cell death both by early ER accumulation leading to an exaggerated unfolded protein response and by enhanced deposition of cellular aggregates associated with proteasome dysfunction.
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PMID:A surfactant protein C precursor protein BRICHOS domain mutation causes endoplasmic reticulum stress, proteasome dysfunction, and caspase 3 activation. 1577 95

The ubiquitin-proteasome system plays a critical role in the regulation of programmed cell death. Proteasome inhibitors induce apoptosis in various cancer cells and have antitumor effects in murine tumor models. In the present study, we investigated whether the cell-permeable proteasome inhibitor MG132 (carbobenzoxyl-L-leucyl-L-leucyl-L-leucinal) reduced the growth of a human pancreatic cancer cell line through induction of apoptosis in vitro. The effects of MG132 (0.125-1.000 microM) on the growth of the human pancreatic cancer cell line BxPC-3 were analyzed by cell count and MTT assay. Apoptosis was determined by FACS analysis after annexin V and propidium iodide staining and the enrichment of intracellular nucleosomes. The proteasome inhibitor MG132 decreased cell growth of the human pancreatic cancer cell line BxPC-3 in a dose- and time-dependent manner. This effect was at least in part mediated by the induction of apoptosis. A combination therapy with standard cytotoxic agents and proteasome inhibitors could potentially be a novel therapeutic strategy in treatment of pancreatic cancer.
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PMID:The proteasome inhibitor MG132 induces apoptosis in human pancreatic cancer cells. 1627 69

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