Glycogen synthase kinase-3beta mediates endoplasmic reticulum stress-induced lysosomal apoptosis in leukemia.
ABSTRACT Glycogen synthase kinase (GSK)-3beta may modulate endoplasmic reticulum (ER) stress-induced apoptosis; however, the mechanism remains unclear. Our data showed that human monocytic leukemia/lymphoma U937 and acute myeloid leukemia HL-60, but not chronic myeloid leukemia K562, cells were susceptible to apoptosis induced by ER stressor tunicamycin, a protein glycosylation inhibitor. Tunicamycin caused early activation of caspase-2, -3, -4, and -8, followed by apoptosis, whereas caspase-9 was slowly activated. Inhibiting caspase-2 reduced activation of caspase-8 and -3 but had no effect on caspase-4. Tunicamycin induced apoptosis independently of the mitochondrial pathway but caused lysosomal destabilization followed by lysosomal membrane permeabilization (LMP), cathepsin B relocation from lysosomes to the cytosol, and caspase-8 and -3 activation. It is notable that caspase-2 mediated lysosomal destabilization. Inhibiting GSK-3beta comprehensively reduced lysosomal apoptosis after caspase-2 inhibition. Unlike U937 and HL-60 cells, K562 cells showed nonresponsive ER stress and failure of activation of GSK-3beta and caspase-2 in response to tunicamycin. Activating GSK-3beta caused K562 cells to be susceptible to tunicamycin-induced apoptosis. Taken together, we show that GSK-3beta exhibits a mechanism of ER stress-induced lysosomal apoptosis in leukemia involving caspase-2-induced LMP and cathepsin B relocation, which result in caspase-8 and -3 activation.
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ABSTRACT: Infection with dengue virus (DENV) causes both mild dengue fever and severe dengue diseases, such as dengue hemorrhagic fever and dengue shock syndrome. The pathogenic mechanisms for DENV are complicated, involving viral cytotoxicity, immunopathogenesis, autoimmunity, and underlying host diseases. Viral load correlates with disease severity, while the antibody-dependent enhancement of infection largely determines the secondary effects of DENV infection. Epidemiological and experimental studies have revealed an association between the plasma levels of interleukin (IL)-10, which is the master anti-inflammatory cytokine, and disease severity in patients with DENV infection. Based on current knowledge of IL-10-mediated immune regulation during infection, researchers speculate an emerging role for IL-10 in clinical disease prognosis and dengue pathogenesis. However, the regulation of dengue pathogenesis has not been fully elucidated. This review article discusses the regulation and implications of IL-10 in DENV infection. For future strategies against DENV infection, manipulating IL-10 may be an effective antiviral treatment in addition to the development of a safe dengue vaccine.Journal of Biomedical Science 06/2013; 20(1):40. · 2.46 Impact Factor
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ABSTRACT: Schweinfurthins are potent inhibitors of cancer cell growth, especially against human central nervous system tumor lines such as SF-295 cells. However, the mechanisms through which these compounds impede cell growth are not fully understood. In an effort to understand the basis for the effects of schweinfurthins, we present a fluorescent schweinfurthin, 3-deoxyschweinfurthin B-like p-nitro-bis-stilbene (3dSB-PNBS), which displays biological activity similar to that of 3-deoxyschweinfurthin B (3dSB). These two schweinfurthins retain the unique differential activity of the natural schweinfurthins, as evidenced by the spindle-like morphological changes induced in SF-295 cells and the unaltered appearance of human lung carcinoma A549 cells. We demonstrate that incubation with 3dSB or 3dSB-PNBS results in cleavage of poly-ADP-ribose polymerase (PARP) and caspase-9, both markers of apoptosis. Coincubation of 3dSB or 3dSB-PNBS with the caspase-9 inhibitor (Z)-Leu-Glu(O-methyl)-His-Asp(O-methyl)-fluoromethylketone prevents PARP cleavage. Therapeutic agents that induce apoptosis often activate cellular stress pathways. A marker for multiple stress pathways is the phosphorylation of eukaryotic initiation factor 2α, which is phosphorylated in response to 3dSB and 3dSB-PNBS treatment. Glucose-regulated protein 78 and protein disulfide isomerase, both endoplasmic reticulum chaperones, are up-regulated with schweinfurthin exposure. Using the fluorescent properties of 3dSB-PNBS and dimethoxyphenyl-p-nitro-bis-stilbene (DMP-PNBS), a control compound, we show that the intracellular levels of 3dSB-PNBS are higher than those of Rhodamine 123 or DMP-PNBS in SF-295 and A549 cells.Molecular pharmacology 03/2012; 82(1):9-16. · 4.53 Impact Factor
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ABSTRACT: HeLa cells treated with celastrol, a natural compound with inhibitive effect on proteasome, exhibited increase in apoptotic rate and characteristics of apoptosis. To clarify the signal network activated by celastrol to induce apoptosis, both the direct target proteins and undirect target proteins of celastrol were searched in the present study. Proteasome catalytic subunit β1 was predicted by computational analysis to be a possible direct target of celastrol and confirmed by checking direct effect of celastrol on the activity of recombinant human proteasome subunit β1 in vitro. Undirect target-related proteins of celastrol were searched using proteomic studies including two-dimensional electrophoresis (2-DE) analysis and iTRAQ-based LC-MS analysis. Possible target-related proteins of celastrol such as endoplasmic reticulum protein 29 (ERP29) and mitochondrial import receptor Tom22 (TOM22) were found by 2-DE analysis of total cellular protein expression profiles. Further study showed that celastrol induced ER stress and ER stress inhibitor could ameliorate cell death induced by celastrol. Celastrol induced translocation of Bax into the mitochondria, which might be related to the upregulation of BH-3-only proteins such as BIM and the increase in the expression level of TOM22. To further search possible target-related proteins of celastrol in ER and ER-related fractions, iTRAQ-based LC-MS method was use to analyze protein expression profiles of ER/microsomal vesicles-riched fraction of cells with or without celastrol treatment. Based on possible target-related proteins found in both 2-DE analysis and iTRAQ-based LC-MS analysis, protein-protein interaction (PPI) network was established using bioinformatic analysis. The important role of glycogen synthase kinase-3β (GSK3β) in the signal cascades of celastrol was suggested. Pretreatment of LiCL, an inhibitor of GSK3β, could significantly ameliorate apoptosis induced by celastrol. On the basis of the results of the present study, possible signal network of celastrol activated by celastrol leading to apoptosis was predicted.Cell Death & Disease 01/2013; 4:e715. · 6.04 Impact Factor