Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P08758 (annexin V)
 9,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytoplasmic acidification is now recognized as a feature of apoptosis in a variety of systems. However, its relation to other events in the process of apoptosis is not yet characterized. In this work, we examined the effect of BCL-2 overexpression on acidification mediated by cycloheximide treatment or Fas ligation in Jurkat T-lymphoblasts. We find that BCL-2 overexpression attenuates cytoplasmic acidification and apoptosis detected by annexin V labeling. Acidification and phosphatidylserine externalization were found to occur concurrently. We also examined the requirement for protease activation for cytoplasmic acidification to occur and found that inhibition of interleukin-1beta converting enzyme/CED-3 family proteases (using carbobenzoxy-Val-Ala-Asp-fluoromethylketone, an inhibitor of these proteases) prevents acidification and apoptosis mediated by Fas ligation. These studies suggest that BCL-2 acts at a point upstream of acidification and that protease activation is also upstream of acidification.
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PMID:Events in apoptosis. Acidification is downstream of protease activation and BCL-2 protection. 866 7

A detailed kinetic analysis of three extranuclear end points of apoptosis, phosphatidylserine exposure, alpha-fodrin degradation, and plasma membrane blebbing, was performed and compared with nuclear fragmentation and the activation of the interleukin-1beta-converting enzyme (ICE)-like proteases in Jurkat T lymphocytes stimulated by anti-Fas monoclonal antibody (anti-Fas mAb) and in monocytic U937 cells stimulated by tumor necrosis factor (TNF) and cycloheximide. Phosphatidylserine exposure was quantitated by plasma clotting time, as well as annexin V-fluorescein isothiocyanate binding, and the ICE-like protease activity was examined by the cleavage of a specific fluorogenic peptide substrate Ac-Asp-Glu-Val-Asp-amino-4-methylcoumarin. VAD-chloromethylketone (VAD-cmk), an inhibitor of ICE-like proteases, effectively inhibited ICE-like activity in both cell types studied, whereas the calpain inhibitor calpeptin was ineffective. VAD-cmk also effectively inhibited all three extranuclear events, as well as nuclear fragmentation, in Jurkat cells stimulated by anti-Fas monoclonal antibody, indicating that ICE-like proteases play an important role in the regulation of this apoptotic system. Calpain inhibitors were ineffective in this system. TNF-induced extranuclear and nuclear changes in U937 cells were inhibited by calpeptin but were not as effectively inhibited by VAD-cmk as in Jurkat cells. This suggests that ICE-like enzymes predominate in anti-Fas monoclonal antibody-stimulated Jurkat cells, whereas proteases affected by calpain inhibitors as well as the ICE-like enzymes are involved in the signaling of apoptotic events in TNF-induced U937 cells. Importantly, the two apoptotic systems seem to be regulated by different proteases.
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PMID:Protease involvement in fodrin cleavage and phosphatidylserine exposure in apoptosis. 894 Jan 3

Many parallel processes occur during the final stages of apoptosis. It is not clear which of these processes occur in all or most models of apoptosis and which occur only in some. In addition, the temporal relationship of these events is not always well understood. Correlated flow cytometric measurements were used to address these questions. Several models of apoptosis were studied, including thymocytes treated with dexamethasone. MOLT-4 cells treated with etoposide, U937 cells treated with anti-Fas, HL-60 cells treated with camptothecin, Raji cells grown in low serum, and aged neutrophils. All models showed a decrease in LDS-751 and fluorescein diacetate (FDA) staining, an increase in staining with dihydrorhodamine 123 (dhR123) or dihydroethidium, and an acidification of the cytoplasm. In each model, these changes were highly correlated, appearing simultaneously as multiparameter measurements. Changes in membrane status detected with merocyanin 540 (MC540) and annexin V behaved differently. A population with LDS-751 and FDA changes but without annexin V or MC540 changes could be demonstrated in some models. Several models did not show any change in annexin V binding, and HL-60 did not show a change in MC540 binding during apoptosis. The loss of cell surface antigens (CD45 and CD16) from aged neutrophils occurred in the entire LDS-751 and FDA dim population, even though other membrane changes (including the appearance of annexin V binding sites) were only apparent in a subset of these cells. These results suggest a model for the ordering of some of the terminal processes in apoptosis, with annexin V and MC540 changes trailing other events in apoptosis. These results confirm the need for caution in using a single-parameter measurement as an indicator of apoptosis for any new model being studied.
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PMID:Correlated flow cytometric analysis of terminal events in apoptosis reveals the absence of some changes in some model systems. 922 11

Phosphatidylserine (PS), ordinarily sequestered in the plasma membrane inner leaflet, appears in the outer leaflet during apoptosis, where it triggers non-inflammatory phagocytic recognition of the apoptotic cell. The mechanism of PS appearance during apoptosis is not well understood but has been associated with loss of aminophospholipid translocase activity and nonspecific flip-flop of phospholipids of various classes. The human leukemic cell line HL-60, the T cell line Jurkat, and peripheral blood neutrophils, undergoing apoptosis induced either with UV irradiation or anti-Fas antibody, were probed in the cytofluorograph for (i) surface PS using fluorescein isothiocyanate-labeled annexin V, (ii) PS uptake by the aminophospholipid translocase using [6-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino] caproyl] (NBD)-labeled PS, (iii) nonspecific uptake of phospholipids (as a measure of transbilayer flip-flop) using NBD-labeled phosphatidylcholine, and (iv) the appearance of hypodiploid DNA. In all three types of cells undergoing apoptosis, the appearance of PS followed loss of aminophospholipid translocase and was accompanied by nonspecific phospholipid flip-flop. Importantly, however, in the absence of extracellular calcium, the appearance of PS was completely inhibited despite DNA fragmentation and loss of aminophospholipid translocase activity, the latter demonstrating that loss of the translocase is insufficient for PS appearance during apoptosis. Furthermore, while both the appearance of PS and nonspecific phospholipid uptake demonstrated identical extracellular calcium requirements with an ED50 of nearly 100 microM, the magnitude of PS appearance depended on the level of aminophospholipid translocase activity. Taken together, the data strongly suggest that while nonspecific flip-flop is the driving event for PS appearance in the plasma membrane outer leaflet, aminophospholipid translocase activity ultimately modulates its appearance.
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PMID:Appearance of phosphatidylserine on apoptotic cells requires calcium-mediated nonspecific flip-flop and is enhanced by loss of the aminophospholipid translocase. 933 82

Ag recognition is an essential component for an effective T cell response. However, T cell activation is also subject to additional regulation by accessory molecules. CD28 provides essential costimulatory signals that allow T cells to proliferate, whereas molecules such as CTLA-4 and CD95 (Fas) appear to be negative regulators. Currently, which outcome predominates under conditions of antigenic challenge is poorly understood. In particular it has been suggested that one consequence of antigenic activation of T cells is the up-regulation of both CD95 and CD95 ligand, thereby exposing activated T cells to apoptotic death. We have investigated this possibility in normal human peripheral blood T cells triggered by the superantigen SEB either in the presence of endogenous APCs or transfectants expressing DR4 and CD80. In either case, we find that such activation does not expose the majority of T cells to anti-CD95-induced apoptosis as detected by annexin V externalization and DNA fragmentation. Furthermore, by phenotypically identifying, by flow cytometry, those cells that received both antigenic and costimulatory signals from those cells that did not, we observed that CD95-induced apoptosis was not seen in activated T cells receiving Ag and costimulatory signals via CD28. However, while not all T cells were stimulated by superantigen, CD95 expression was found to be homogeneously up-regulated, suggesting a mechanism whereby bystander cells might be made susceptible to CD95-induced death. We conclude that antigenic activation of T cells via the TCR and CD28 engagement provides protection from CD95-induced apoptosis.
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PMID:Activation of human T cells with superantigen (staphylococcal enterotoxin B) and CD28 confers resistance to apoptosis via CD95. 949 43

The pathogenic role of antiendothelial cell antibodies (AECA) remains unclear. They are frequently associated with antibodies to anionic phospholipids (PL), such as phosphatidylserine (PS), which is difficult to reconcile with the distribution of PL molecular species within the plasma membrane. Since it is already known that PS is transferred to the outer face of the membrane as a preclude to apoptosis, the possibility exists that apoptosis is initiated by AECA. AECA-positive/anti-PL antibody-negative sera from eight patients with systemic sclerosis (SS) and 21 control patients were evaluated. Endothelial cells (EC) were incubated with AECA and the exposure of PS was established through the binding of annexin V. Hypoploid cell enumeration, DNA fragmentation, and optical and ultrastructural analyses of EC were used to confirm apoptosis. Incubation of EC with AECA derived from six of eight patients with SS led to the expression of PS on the surface of the cells. This phenomenon was significantly more frequent in SS (P < 0.04) than in control diseases. The redistribution of plasma membrane PS preceded other events associated with apoptosis: hypoploidy, DNA fragmentation, and morphology characteristic for apoptosis. Apoptosis-inducing AECA did not recognize the Fas receptor. We conclude that AECA may be pathogenic by inducing apoptosis.
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PMID:The binding of some human antiendothelial cell antibodies induces endothelial cell apoptosis. 959 58

One of the earliest events in programmed cell death is the externalization of phosphatidylserine, a membrane phospholipid normally restricted to the inner leaflet of the lipid bilayer. Annexin V, an endogenous human protein with a high affinity for membrane bound phosphatidylserine, can be used in vitro to detect apoptosis before other well described morphologic or nuclear changes associated with programmed cell death. We tested the ability of exogenously administered radiolabeled annexin V to concentrate at sites of apoptotic cell death in vivo. After derivatization with hydrazinonicotinamide, annexin V was radiolabeled with technetium 99m. In vivo localization of technetium 99m hydrazinonicotinamide-annexin V was tested in three models: fuminant hepatic apoptosis induced by anti-Fas antibody injection in BALB/c mice; acute rejection in ACI rats with transplanted heterotopic PVG cardiac allografts; and cyclophosphamide treatment of transplanted 38C13 murine B cell lymphomas. External radionuclide imaging showed a two- to sixfold increase in the uptake of radiolabeled annexin V at sites of apoptosis in all three models. Immunohistochemical staining of cardiac allografts for exogenously administered annexin V revealed intense staining of numerous myocytes at the periphery of mononuclear infiltrates of which only a few demonstrated positive apoptotic nuclei by the terminal deoxynucleotidyltransferase-mediated UTP end labeling method. These results suggest that radiolabeled annexin V can be used in vivo as a noninvasive means to detect and serially image tissues and organs undergoing programmed cell death.
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PMID:In vivo detection and imaging of phosphatidylserine expression during programmed cell death. 960 Sep 68

Signals from the IL-7R are essential for normal thymocyte development. We isolated thymocytes from early developmental stages and observed that suspensions of pro-T1, -T2, and -T3 cells rapidly died in culture. Addition of IL-7 promoted their survival, but did not induce cell division. Pro-T4 cells did not undergo rapid cell death, and their survival was therefore independent of IL-7. Death in the absence of IL-7 showed the hallmarks of apoptosis, including DNA fragmentation and annexin V binding; however, caspase inhibitors blocked DNA fragmentation, but did not block cell death. The trophic effect of IL-7 was partially inhibited by blocking protein synthesis. The p53 pathway was not involved in this death pathway, since pro-T cells from p53-/- mice also underwent cell death in the absence of IL-7. The Fas/Fas ligand pathway was not involved in cell death, since Fas-deficient pro-T cells died normally in the absence of IL-7, anti-Fas Abs did not protect cells from death in the absence of IL-7, and Fas expression was undetectable on cells at these stages. The IL-7 trophic affect correlated with increased intracellular levels of Bcl-2 and decreased levels of Bax, whereas no Bcl-X(L), Bcl-w, or Bad was detectable. Thus, maintaining a favorable Bcl-2/Bax ratio may account for the trophic action of IL-7.
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PMID:The trophic action of IL-7 on pro-T cells: inhibition of apoptosis of pro-T1, -T2, and -T3 cells correlates with Bcl-2 and Bax levels and is independent of Fas and p53 pathways. 963 82

Upon transforming growth factor-beta (TGF-beta) treatment, Ramos cells, a B-cell lymphoma cell line, undergo apoptosis, as measured by annexin V labeling, DNA fragmentation, and propidium iodide staining. Apoptosis could be observed by 24 h after TGF-beta exposure and occurred before the development of a significant blockage of cell cycle progression. TGF-beta-mediated apoptosis was also accompanied by a strong induction of caspase-3 subfamily activity. Incubation of cells with the caspase inhibitor Z-VAD.FMK at 20 microM, but not at 10 microM, prevented TGF-beta-induced apoptosis from occurring. By comparison, caspase-3 subfamily activity was 87% inhibited at 10 microM Z-VAD.FMK and completely inhibited at 20 microM. Because of TGF-beta's well-established role of regulating gene transcription, the mRNA levels for proteins associated with apoptosis (Fas- and Fas-associated proteins, Bcl-2 family members, IAP proteins, and I kappa B) were also studied. After 24 h of TGF-beta treatment, the most significant mRNA changes occurred with Bcl-XL (two-fold decrease) and Bik (twofold increase). TGF-beta treatment also resulted after 48 h in a fivefold decrease in Bcl-XL protein levels, based on immunoblotting analysis. Therefore, TGF-beta-mediated apoptosis involves the activation of caspases. In addition, TGF-beta transcriptionally regulates Bcl-2 family members, Bcl-XL and Bik, to further influence the apoptosis process.
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PMID:Transforming growth factor-beta-mediated apoptosis in the Ramos B-lymphoma cell line is accompanied by caspase activation and Bcl-XL downregulation. 966 22

Apoptosis of neutrophils plays a critical role in the resolution of acute inflammation. Neutrophils from human peripheral blood express Fas (CD95) and are sensitive to Fas ligand (FasL)/Fas-mediated apoptosis. Mice carrying spontaneous mutations in the genes for fas ligand (B6/gld) or fas (B6/lpr) were used to assess the role of FasL/Fas in the kinetics and magnitude of neutrophil extravasation to the thioglycolate (TG)-inflamed peritoneum and in the spontaneous apoptosis of TG-elicited neutrophils. The results showed that TG-elicited neutrophils (defined by flow cytometry as GR-1/Ly-6G(hi) cells) from normal (B6) and B6/gld mice, but not from the Fas-deficient B6/lpr mice, express high levels of Fas. The TG-elicited neutrophil response began at 2 h, peaked at 4 h, and subsided by 24-48 h after TG administration in all three strains. However, the response was more prolonged in B6 mice, such that B6/gld and B6/lpr mice had fewer neutrophils at 6 h after TG administration than did B6 mice. Further studies showed that 4 h TG-elicited neutrophils from B6, B6/gld and B6/lpr mice undergo apoptosis in vitro at similar rates (as assessed through flow cytometry by the decrease in forward angle light-scatter and externalization of phosphatidylserine (PS; as detected by Annexin V-FITC) that occur as neutrophils undergo apoptosis). Fas expression was down-regulated on apoptotic neutrophils in conjunction with maximal PS externalization and decreased forward angle light-scatter. Collectively, these findings suggest that FasL/Fas-mediated apoptosis is not essential in regulating the lifespan of neutrophils during an acute inflammatory response. The abbreviated inflammatory response observed in FasL/Fas-deficient mice is likely to be a secondary effect of the gld/lpr autoimmune/lymphoproliferative syndrome, and not a direct effect of FasL/Fas on the ability of inflammatory neutrophils to undergo apoptosis.
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PMID:Fas ligand (gld)- and Fas (lpr)-deficient mice do not show alterations in the extravasation or apoptosis of inflammatory neutrophils. 973 65


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