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Intrinsic Apoptotic Pathway (intrinsic + apoptotic_pathway)
Selected AbstractsProteasome inhibitor-induced apoptosis in human monocyte-derived dendritic cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 3 2006Alessio Nencioni Dr. Abstract Proteasome inhibitors possess potent antitumor activity against a broad spectrum of human malignancies. However, the effects of these compounds on the immune system still have to be clearly determined. In the present study, we have investigated the effects of proteasome inhibitors on dendritic cells (DC), antigen-presenting cells playing a key role in the initiation of immune responses. Exposure to the proteasome inhibitors bortezomib, MG132 or epoxomicin was found to promote apoptosis of human monocyte-derived DC and to reduce the yield of viable DC when given to monocytes early during differentiation to DC. DC apoptosis via proteasome inhibition was accompanied by mitochondria disruption and subsequent activation of the caspase cascade. Up-regulation and intracellular redistribution of Bcl-2-associated X,protein (Bax), a pro-apoptotic Bcl-2 family protein, were observed in DC treated with these compounds and represent a suitable mechanism leading to activation of the intrinsic apoptotic pathway. Finally, active protein synthesis was found to represent an upstream prerequisite for DC apoptosis induced by proteasome inhibitors, since the translation inhibitor cycloheximide blocked all of the steps of the observed apoptotic response. In conclusion, induction of apoptosis in DC may represent a novel mechanism by which proteasome inhibitors affect the immune response at the antigen-presenting cell level. [source] Maintenance of the relative proportion of oligodendrocytes to axons even in the absence of BAX and BAKEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2009Kumi Kawai Abstract Highly purified oligodendroglial lineage cells from mice lacking functional bax and bak genes were resistant to apoptosis after in-vitro differentiation, indicating an essential role of the intrinsic apoptotic pathway in apoptosis of oligodendrocytes in the absence of neurons (axons) and other glial cells. These mice therefore provide a valuable tool with which to evaluate the significance of the intrinsic apoptotic pathway in regulating the population sizes of oligodendrocytes and oligodendroglial progenitor cells. Quantitative analysis of the optic nerves and the dorsal columns of the spinal cord revealed that the absolute numbers of mature oligodendrocytes immunolabeled for aspartoacylase and adult glial progenitor cells expressing NG2 chondroitin sulfate proteoglycan were increased in both white matter tracts of adult bax/bak -deficient mice and, to a lesser extent, bax -deficient mice, except that there was no increase in NG2-positive progenitor cells in the dorsal columns of these strains of mutant mice. These increases in mature oligodendrocytes and progenitor cells in bax/bak -deficient mice were unexpectedly proportional to increases in numbers of axons in these white matter tracts, thus retaining the oligodendroglial lineage to axon ratios of at most 1.3-fold of the physiological numbers. This is in contrast to the prominent expansion in numbers of neural precursor cells in the subventricular zones of these adult mutant mice. Our study indicates that homeostatic control of cell number is different for progenitors of the oligodendroglial and neuronal lineages. Furthermore, regulatory mechanism(s) operating in addition to apoptotic elimination through the intrinsic pathway, appear to prevent the overproduction of highly mitotic oligodendroglial progenitor cells. [source] ARC protects rat cardiomyocytes against oxidative stress through inhibition of caspase-2 mediated mitochondrial pathwayJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2006Yi-Qiang Zhang Abstract Apoptosis repressor with a CARD domain (ARC) has been demonstrated to protect heart cells against ischemia/reperfusion (I/R) injury. In this study, we investigated the mechanism by which ARC protects heart cells against oxidative stress. We monitored the extent of apoptosis and activity of multiple components of the intrinsic apoptotic pathway in rat cardiac myoblast cell line H9c2 with either reduced or increased expression of ARC during oxidative stress. Overexpression of ARC-inhibited oxidative stress-induced caspase-2/3 activation, cytochrome c release, and translocation of Bax to mitochondria. Furthermore, phosphorylation of ARC at threonine 149 was found to be critical to its function. ARC containing a T149A mutation failed to translocate to mitochondria, did not inhibit caspase-2 activation, and had a dominant negative effect against the protective effect of endogenous ARC during oxidative stress. In addition, wild-type ARC but not the T149A mutant inhibited cell death induced by overexpression of caspase-2. Using a yeast two-hybrid (YTH) screening approach and co-immunoprecipitation (Co-IP), we found that protein phosphatase 2C (PP2C) interacted with ARC and that PP2C mediated-dephosphorylation of ARC inhibited its anti-apoptotic activity. Eliminating either the N-terminal CARD domain or the C-terminal P/E domain also abolished the anti-apoptotic function of ARC, suggesting that full-length ARC is required for its apoptotic inhibition. These results indicate that ARC plays an important role in protection of H9c2 cells against oxidative stress-induced apoptosis by phosphorylation-dependent suppression of the mitochondria-mediated intrinsic pathway, partially initiated through the activation of caspase-2. J. Cell. Biochem. 99: 575,588, 2006. © 2006 Wiley-Liss, Inc. [source] Proteome analysis of apoptosis signaling by S -trityl- L -cysteine, a potent reversible inhibitor of human mitotic kinesin Eg5PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 2 2008Frank Kozielski Abstract Mitotic kinesins represent potential drug targets for anticancer chemotherapy. Inhibitors of different chemical classes have been identified that target human Eg5, a kinesin responsible for the establishment of the bipolar spindle. One potent Eg5 inhibitor is S -trityl- L -cysteine (STLC), which arrests cells in mitosis and exhibits tumor growth inhibition activity. However, the underlying mechanism of STLC action on the molecular level is unknown. Here, cells treated with STLC were blocked in mitosis through activation of the spindle assembly checkpoint as shown by the phosphorylated state of BubR1 and the accumulation of mitosis specific phosphorylation on histone H3 and aurora A kinase. Using live cell imaging, we observed prolonged mitotic arrest and subsequent cell death after incubation of GFP-,-tubulin HeLa cells with STLC. Activated caspase-9 occurred before cleavage of caspase-8 leading to the accumulation of the activated executioner caspase-3 suggesting that STLC induces apoptosis through the intrinsic apoptotic pathway. Proteome analysis following STLC treatment revealed 33 differentially regulated proteins of various cellular processes, 31 of which can be linked to apoptotic cell death. Interestingly, four identified proteins, chromobox protein homolog, RNA-binding Src associated in mitosis 68,kDa protein, stathmin, and translationally controlled tumor protein can be linked to mitotic and apoptotic processes. [source] Triptolide abrogates oncogene FIP1L1-PDGFR, addiction and induces apoptosis in hypereosinophilic syndromeCANCER SCIENCE, Issue 11 2009Yanli Jin The pathogenesis of hypereosinophilic syndrome (HES) in some patients is highly dependent on FIP1-Like-1 (FIP1L1),platelet-derived growth factor receptor alpha (PDGFR,), which can generate sustained activation signaling to maintain a cell malignant phenotype. HES usually shows good response to the tyrosine kinase inhibitor imatinib, but mutations in FIP1L1-PDGFR, (e.g. T674I) can confer acquired resistance to imatinib. An alternative therapeutic strategy other than with tyrosine kinase inhibitors is needed to overcome acquired drug resistance. We hypothesized that switching off the crucial chimeric oncoprotein FIP1L1-PDGFR, on which HES cells depend, should have deleterious effects on the cancer cells. We used low concentrations of triptolide, a transcription inhibitor, to shut down the expression of FIP1L1-PDGFR,. EOL-1 cells and BaF3 cells expressing wild-type or T674I FIP1L1-PDGFR, were treated with triptolide, and signaling pathways, cell cycling, and apoptosis were analyzed by RT-PCR, immunoblotting, and flow cytometry, respectively. The results revealed that at nanomolar concentrations triptolide decreased the levels of mRNA and protein of FIP1L1-PDGFR, and the growth of the neoplastic cells, regardless of the mutational status of PDGFR,. Triptolide also downregulated the signaling molecules Stat3, Akt, and Erk1/2, which are downstream from PDGFR,, and induced G1 cell-cycle arrest. Triptolide time- and dose-dependently induced apoptosis by decreasing the anti-apoptotic proteins Mcl-1 and Bcl-XL,triggering the intrinsic apoptotic pathway. In conclusion, triptolide has potent activity against malignant cells in HES bearing FIP1L1-PDGFR,, regardless of its mutational status that confer acquired resistance to imatinib. Our results suggest that triptolide may be a promising agent in the treatment of HES. (Cancer Sci 2009; 00: 000,000) [source] Acyl-CoA synthetase as a cancer survival factor: its inhibition enhances the efficacy of etoposideCANCER SCIENCE, Issue 8 2009Tetsuo Mashima Lipid metabolism is often elevated in cancer cells and plays an important role in their growth and malignancy. Acyl-CoA synthetase (ACS), which converts long-chain fatty acids to acyl-CoA, is overexpressed in various types of cancer. However, the role of ACS in cancer remains unknown. Here, we found that ACS enzyme activity is required for cancer cell survival. Namely, the ACS inhibitor Triacsin c induced massive apoptosis in glioma cells while this cell death was completely suppressed by overexpression of ACSL5, the Triacsin c,resistant ACS isozyme, but not by overexpression of a catalytically inactive ACSL5 mutant. ACS inhibition by Triacsin c markedly potentiated the Bax-induced intrinsic apoptotic pathway by promoting cytochrome c release and subsequent caspase activation. These effects were abrogated by ACSL5 overexpression. Correspondingly, ACS inhibition synergistically potentiated the glioma cell death induced by etoposide, a well-known activator of apoptosis. Furthermore, in a nude mouse xenograft model, Triacsin c at a non-toxic dose enhanced the antitumor efficacy of a low-dose chemotherapy with etoposide. These results indicate that ACS is an apoptosis suppressor and that ACS inhibition could be a rational strategy to amplify the antitumor effect of etoposide. (Cancer Sci 2009) [source] The initiator caspase, caspase-10,, and the BH-3-only molecule, Bid, demonstrate evolutionary conservation in Xenopus of their pro-apoptotic activities in the extrinsic and intrinsic pathwaysGENES TO CELLS, Issue 7 2006Katsuya Kominami Two major apoptotic signaling pathways have been defined in mammals, the extrinsic pathway, initiated by ligation of death receptors, and the intrinsic pathway, triggered by cytochrome c release from mitochondria. Here, we identified and characterized the Xenopus homologs of caspase-10 (xCaspase-10,), a novel initiator caspase, and Bid (xBid), a BH3-only molecule of the Bcl-2 family involved in both the extrinsic and intrinsic pathways. Exogenous expression of these molecules induced apoptosis of mammalian cells. By biochemical and cytological analyses, we clarified that xCaspase-10, and xBid exhibit structural and functional similarities to their mammalian orthologues. We also detected xCaspase-10, and xBid transcripts during embryogenesis by whole-mount in situ hybridization and RT-PCR analysis. Microinjection of mRNA encoding a protease-defect xCaspase-10, mutant into embryos resulted in irregular development. Enforced expression of active xBid induced cell death in developing embryos. Using transgenic frogs established to allow monitoring of caspase activation in vivo, we confirmed that this form of cell death is caspase-dependent apoptosis. Thus, we demonstrated that the machinery governing the extrinsic and intrinsic apoptotic pathways are already established in Xenopus embryos. Additionally, we propose that the functions of the initiator caspase and BH3-only molecule are evolutionarily conserved in vertebrates, functioning during embryonic development. [source] Gene expression of anti- and pro-apoptotic proteins in malignant and normal plasma cellsBRITISH JOURNAL OF HAEMATOLOGY, Issue 1 2009Michel Jourdan Summary The survival of malignant plasma cells is a key event in disease occurrence, progression and chemoresistance. Using DNA-microarrays, we analysed the expression of genes coding for 58 proteins linked with extrinsic and intrinsic apoptotic pathways, caspases and inhibitor of apoptosis proteins. We considered six memory B cells (MBC), seven plasmablasts (PPC), seven bone marrow plasma cells (BMPC) and purified myeloma cells (MMC) from 92 newly-diagnosed patients. Forty out of the 58 probe sets enabled the separation of MBC, PPC and BMPC in three homogeneous clusters, characterized by an elevated expression of TNFRSF10A, TNFRSF10B, BCL2A1, CASP8, CASP9 and PMAIP1 genes for MBC, of FAS, FADD, AIFM1, BIRC5, CASP CASP2, CASP3 and CASP6 for PPC and of BCL2, MCL1, BID, BIRC3 and XIAP for BMPC. Thus, B cell differentiation was associated with change of expression of pro-apoptotic and anti-apoptotic genes. Regarding MMC, the major finding was TRAIL upregulation that might be counteracted by a high osteoprotegerin production by BM stromal cells and a decreased expression of FAS, APAF1 and BNIP3 compared to normal BMPC. Out of the 40 genes, CASP2 and BIRC5 expression in MMC had adverse prognosis in two independent series of previously-untreated patients. [source] Induction of cell apoptosis in non-small cell lung cancer cells by cyclin A1 small interfering RNACANCER SCIENCE, Issue 10 2006Nam Hoon Cho Cyclin A1 and cyclin B1 are overexpressed in various tumors but are present at low levels in normal tissues. Cyclin A1 is restricted to germ cells undergoing meiosis. In order to explore the possibility of using cyclin A1 and cyclin B1 as anticancer targets, we knocked them down in two lung cancer cell lines, H157 and H596, using siRNA. As with cyclin A1 siRNA in lung cancer cell lines, cyclin B1, Cdc2 and CDK2 were all significantly downregulated. The S phase fraction increased significantly, and they eventually underwent apoptosis by way of downregulated intrinsic apoptotic pathways and modulators with upregulated extrinsic apoptotic pathways. Our study suggests that cyclin A1 might be a promising anticancer target specific to lung cancer. (Cancer Sci 2006; 97: 1082,1092) [source] | |||||||||||||