Cell Death & Differentiation

Schwab, J M; Schluesener, H J

doi: 10.1038/sj.cdd.4401487pmid: 15359293

Skoff, R P; Bessert, D A; Cerghet, M; Franklin, M J; Rout, U K; Nave, K-A; Carlock, L; Ghandour, M S; Armant, D R

doi: 10.1038/sj.cdd.4401498pmid: 15375385

Mutations of the myelin proteolipid protein gene (Plp) are associated with excessive programmed cell death (PCD) of oligodendrocytes. We show for the first time that PLP is a molecule ubiquitously expressed in non-neural tissues during normal development, and that the level of native PLP modulates the level of PCD. We analyze three non-neural tissues, and show that native PLP is expressed in trophoblasts, spermatogonia, and cells of interdigital webbing. The non-neural cells that express high levels of native PLP also undergo PCD. The level of PLP expression modulates the level of PCD because mice that overexpress native PLP have increased PCD and mice deficient in PLP have decreased PCD. We show that overexpression of native PLP causes a dramatic acidification of extracellular fluid that, in turn, causes increased PCD. These studies show that the level of native PLP modulates the amount of PCD during normal development via a pH-dependent mechanism.

Sun, E; Gao, Y; Chen, J; Roberts, A I; Wang, X; Chen, Z; Shi, Y

doi: 10.1038/sj.cdd.4401500pmid: 15375386

Cell death through apoptosis plays a critical role in regulating cellular homeostasis. Whether the disposal of apoptotic cells through phagocytosis can actively induce immune tolerance in vivo, however, remains controversial. Here, we report in a rat model that without using immunosuppressants, transfusion of apoptotic splenocytes from the donor strain prior to transplant dramatically prolonged survival of heart allografts. Histological analysis verified that rejection signs were significantly ameliorated. Splenocytes from rats transfused with donor apoptotic cells showed a dramatically decreased response to donor lymphocyte stimulation. Most importantly, blockade of phagocytosis in vivo, either with gadolinium chloride to disrupt phagocyte function or with annexin V to block binding of exposed phosphotidylserine to its receptor on phagocytes, abolished the beneficial effect of transfused apoptotic cells on heart allograft survival. Our results demonstrate that donor apoptotic cells promote specific allograft acceptance and that phagocytosis of apoptotic cells in vivo plays a crucial role in maintaining immune tolerance.

Carvalho, A C P; Sharpe, J; Rosenstock, T R; Teles, A F V; Kowaltowski, A J; Youle, R J; Smaili, S S

doi: 10.1038/sj.cdd.4401508pmid: 15499375

In the present study, we evaluated proapoptotic protein Bax on mitochondria and Ca2+ homeostasis in primary cultured astrocytes. We found that recombinant Bax (rBax, 10 and 100 ng/ml) induces a loss in mitochondrial membrane potential (ΔΨm). This effect might be related to the inhibition of respiratory rates and a partial release of cytochrome c, which may change mitochondrial morphology. The loss of ΔΨm and a selective permeabilization of mitochondrial membranes contribute to the release of Ca2+ from the mitochondria. This was inhibited by cyclosporin A (5 μM) and Ruthenium Red (1 μg/ml), indicating the involvement of mitochondrial Ca2+ transport mechanisms. Bax-induced mitochondrial Ca2+ release evokes Ca2+ waves and wave propagation between cells. Our results show that Bax induces mitochondrial alteration that affects Ca2+ homeostasis and signaling. These changes show that Ca2+ signals might be correlated with the proapoptotic activities of Bax.

Hahn, H P; Pang, M; He, J; Hernandez, J D; Yang, R-Y; Li, L Y; Wang, X; Liu, F-T; Baum, L G

doi: 10.1038/sj.cdd.4401485pmid: 15297883

Galectin-1, a mammalian lectin expressed in many tissues, induces death of diverse cell types, including lymphocytes and tumor cells. The galectin-1 T cell death pathway is novel and distinct from other death pathways, including those initiated by Fas and corticosteroids. We have found that galectin-1 binding to human T cell lines triggered rapid translocation of endonuclease G from mitochondria to nuclei. However, endonuclease G nuclear translocation occurred without cytochrome c release from mitochondria, without nuclear translocation of apoptosis-inducing factor, and prior to loss of mitochondrial membrane potential. Galectin-1 treatment did not result in caspase activation, nor was death blocked by caspase inhibitors. However, galectin-1 cell death was inhibited by intracellular expression of galectin-3, and galectin-3 expression inhibited the eventual loss of mitochondrial membrane potential. Galectin-1-induced cell death proceeds via a caspase-independent pathway that involves a unique pattern of mitochondrial events, and different galectin family members can coordinately regulate susceptibility to cell death.

Kang, Y-C; Kim, K-M; Lee, K-S; Namkoong, S; Lee, S-J; Han, J-A; Jeoung, D; Ha, K-S; Kwon, Y-G; Kim, Y-M

doi: 10.1038/sj.cdd.4401489pmid: 15297884

Serum contains a variety of biomolecules, which play an important role in cell proliferation and survival. We sought to identify the serum factor responsible for mitigating tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis and to investigate its molecular mechanism. TRAIL induced effective apoptosis without serum, whereas bovine serum decreased apoptosis by suppressing cytochrome c release and caspase activation. Indeed, albumin-bound lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) inhibited TRAIL-induced apoptosis by suppressing caspase activation and cytochrome c release. LPA increased phosphatidylinositol 3-kinase (PI3K)-dependent Akt activation, cellular FLICE-inhibitory protein (cFLIP) expression, and Bad phosphorylation, resulting in inhibition of caspase-8 activation and Bad translocation to mitochondria. The antiapoptotic effect of LPA was abrogated by PI3K inhibitor, transfection with dominant-negative Akt, and specific downregulation of cFLIP expression using siRNA and further increased by siRNA-mediated suppression of Bad expression. Moreover, sera from ovarian cancer patients showed more protective effect against TRAIL-induced apoptosis than those from healthy donors, and this protection was suppressed by PI3K inhibitor. Our results indicate that albumin-bound LPA and S1P prevent TRAIL-induced apoptosis by upregulation of cFLIP expression and in part by Bad phosphorylation, through the activation of PI3K/Akt pathway.

Li, C Y; Zhan, Y Q; Xu, C W; Xu, W X; Wang, S Y; Lv, J; Zhou, Y; Yue, P B; Chen, B; Yang, X M

doi: 10.1038/sj.cdd.4401490pmid: 15332117

Erythroid differentiation-associated gene (EDAG) is considered to be a human hematopoiesis-specific gene. Here, we reported that downregulation of EDAG protein in K562 cells resulted in inhibition of growth and colony formation, and enhancement of sensitivity to erythroid differentiation induced by hemin. Overexpression of EDAG in HL-60 cells significantly blocked the expression of the monocyte/macrophage differentiation marker CD11b after pentahydroxytiglia myristate acetate induction. Moreover, overexpression of EDAG in pro-B Ba/F3 cells prolonged survival and increased the expression of c-Myc, Bcl-2 and Bcl-xL in the absence of interleukin-3 (IL-3). Furthermore, we showed that EDAG enhanced the transcriptional activity of nuclear factor-kappa B (NF-κB), and high DNA-binding activity of NF-κB was sustained in Ba/F3 EDAG cells after IL-3 was withdrawn. Inhibition of NF-κB activity resulted in promoting Ba/F3 EDAG cells death. These results suggest that EDAG regulates the proliferation and differentiation of hematopoietic cells and resists cell apoptosis through the activation of NF-κB.

Jabbour, A M; Ho, P-k; Puryer, M A; Ashley, D M; Ekert, P G; Hawkins, C J

doi: 10.1038/sj.cdd.4401501pmid: 15543163

A genetically defined pathway orchestrates the removal of 131 of the 1090 somatic cells generated during the development of the hermaphrodite nematode Caenorhabditis elegans. Regulation of apoptosis is highly evolutionarily conserved and the nematode cell death pathway is a valuable model for studying mammalian apoptotic pathways, the dysregulation of which can contribute to numerous diseases. The nematode caspase CED-3 is ultimately responsible for the destruction of worm cells in response to apoptotic signals, but it must first be activated by CED-4. CED-9 inhibits programmed cell death and considerable data have demonstrated that CED-9 can directly bind and inhibit CED-4. However, it has been suggested that CED-9 may also directly inhibit CED-3. In this study, we used a yeast-based system and biochemical approaches to explore this second potential mechanism of action. While we confirmed the ability of CED-9 to inhibit CED-4, our data argue that CED-9 can not directly inhibit CED-3.

Hofer-Warbinek, R; Schmid, J A; Mayer, H; Winsauer, G; Orel, L; Mueller, B; Wiesner, Ch; Binder, B R; de Martin, R

doi: 10.1038/sj.cdd.4401502pmid: 15389287

We describe here the identification and initial characterization of a novel human gene termed IKIP (I kappa B kinase interacting protein) that is located on chromosome 12 in close proximity to APAF1 (apoptotic protease-activating factor-1). IKIP and APAF1 share a common 488 bp promoter from which the two genes are transcribed in opposite directions. Three IKIP transcripts are generated by differential splicing and alternative exon usage that do not show significant homology to other genes in the databases. Similar to APAF1, expression of IKIP is enhanced by X-irradiation, and both genes are dependent on p53. Moreover, IKIP promotes apoptosis when transfected into endothelial cells. We conclude that IKIP is a novel p53 target gene with proapoptotic function.

Naumann, U; Wischhusen, J; Weit, S; Rieger, J; Wolburg, H; Massing, U; Weller, M

doi: 10.1038/sj.cdd.4401503pmid: 15389288

Alkylphosphocholines (APC) are candidate anticancer agents. We here report that APC induce the formation of large vacuoles and typical features of apoptosis in human glioma cell lines, but not in immortalized astrocytes. APC promote caspase activation, poly(ADP-ribose)-polymerase (PARP) processing and cytochrome c release from mitochondria. Adenoviral X-linked inhibitor of apoptosis (XIAP) gene transfer, or exposure to the caspase inhibitor, benzyloxycarbonyl-Val-Ala-DL-Asp-fluoro-methylketone zVAD-fmk, blocks caspase-7 and PARP processing, but not cell death, whereas BCL-XL blocks not only caspase-7 and PARP processing but also cell death. APC induce changes in ΔΨm in sensitive glioma cells, but not in resistant astrocytes. The changes in ΔΨm are unaffected by crm-A (cowpox serpin – cytokine response modifier protein A), XIAP or zVAD-fmk, but blocked by BCL-XL, and are thus a strong predictor of cell death in response to APC. Free radicals are induced, but not responsible for cell death. APC thus induce a characteristic morphological, BCL-XL-sensitive, apparently caspase-independent cell death involving mitochondrial alterations selectively in neoplastic astrocytic cells.