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Programmed cell death (PCD) is a suicide mechanism adopted by multicellular organisms that is essential for development and resistance to different forms of stress. In plants, PCD is involved from embryogenesis to death of the whole plant. PCD is genetically regulated and the molecular pathways involved in different forms of this process in animals are relatively more understood than in plants. At the morphological level, apoptosis, one of the forms of PCD in animals, and plant PCD have some similarities such as cell shrinkage, shrinkage of the nucleus, and DNA fragmentation. Because morphological characteristics are a product of the genetically encoded PCD mechanism, it is of interest to figure out how much of the apoptotic pathway is shared with plant PCD in terms of the genes involved. Evidence of some level of similarities has been gathered in the last decade, supporting conservation during signaling, regulation, and execution of apoptosis and plant PCD. A continued search into the genomes of plants has provided insights about homologues of apoptosis genes present in plants, and functional analysis provides evidence about which genes are carrying out similar roles during apoptosis and plant PCD. This review is aimed at updating on the progress of plant PCD mechanism research and highlighting some of the similarities and differences between plant and mammalian PCD mechanisms, with special focus on the commonalities. Key words: programmed cell death, apoptosis, caspase-like enzymes, regulation, signaling, execution. La mort cellulaire programmee (MCP) constitue un mecanisme de suicide adopte par les organismes multicellulaires qui est essentielle au developpement et a la resistance a differentes formes de stress. Chez les vegetaux, la MCP est impliquee de l'embryogenese a la mort complete de la plante. La MCP est regulee genetiquement et les sentiers moleculaires impliques dans les differentes formes de ce processus chez les animaux sont relativement mieux compris que chez les plantes. Sur le plan morphologique, l'apoptose, une des formes de MCP chez les animaux, et la MCP chez les vegetaux partagent certaines similarites comme la retraction cellulaire, la retraction nucleaire et la fragmentation de l'ADN. Puisque ces caracteristiques morphologiques sont issues du mecanisme de MCP code genetiquement, il est d'interet de determiner la proportion du sentier d'apoptose qui est partagee avec la MCP des vegetaux en termes de genes impliques. Des preuves d'un certain niveau de similarite ont ete recoltees au cours de la derniere decennie, ce qui appuie la conservation des processus durant la signalisation, la regulation et l'execution de l'apoptose et de la MCP des vegetaux. Une recherche en continu dans les genomes des plantes a donne un apercu des homologues des genes de l'apoptose presents chez les plantes, et l'analyse fonctionnelle permet de determiner quels genes jouent des roles similaires durant l'apoptose et la MCP chez les vegetaux. Cet article de synthese vise a mettre a jour l'information relative a la recherche portant sur la MCP chez les vegetaux, et souligne certaines similarites et differences entre les mecanismes de MCP chez les vegetaux et les mammiferes, et plus particulierement sur les points communs. [Traduit par la Redaction] Mots-cles: mort cellulaire programmee, apoptose, enzymes de type caspase, regulation, signalisation, execution., Introduction Programmed cell death (PCD) is a genetically regulated process responsible for the elimination of undesirable cells in eukaryotes; it is necessary for development and survival. It is also essential [...]

Primary astrocytomas of grade 3 or 4 according to the classification system of the World Health Organization (high-grade astrocytomas or HGAs) are preponderant among adults and are almost invariably fatal despite the use of multimodal therapy. Here we show that the juvenile brain has an endogenous defense mechanism against HGAs. Neural precursor cells (NPCs) migrate to HGAs, reduce glioma expansion and prolong survival time by releasing endovanilloids that activate the vanilloid receptor (transient receptor potential vanilloid subfamily member-1 or TRPV1) on HGA cells. TRPV1 is highly expressed in tumor and weakly expressed in tumor-free brain. TRPV1 stimulation triggers tumor cell death through the branch of the endoplasmic reticulum stress pathway that is controlled by activating transcription factor-3 (ATF3). The antitumorigenic response of NPCs is lost with aging. NPC-mediated tumor suppression can be mimicked in the adult brain by systemic administration of the synthetic vanilloid arvanil, suggesting that TRPV1 agonists have potential as new HGA therapeutics., Somatic mutant neural stem cells and NPCs are thought to be the source of HGAs, one of the most aggressive forms of tumors of the central nervous system (CNS) (1). [...]

Prolonged endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) have been linked to apoptosis via several mechanisms, including increased expression of C/EBP homologous protein (Chop). Increased long-chain fatty acids, in particular saturated fatty acids, induce ER stress, Chop expression, and apoptosis in liver cells. The first aim of the present study was to determine the role of Chop in lipid-induced hepatocyte cell death and liver injury induced by a methionine-choline-deficient diet. Albumin-bound palmitate increased Chop gene and protein expression in a dose-dependent fashion in H4IIE liver cells, siRNA-mediated silencing of Chop in H4IIE liver cells reduced thapsigargin-mediated cell death by ~40% and delayed palmitate-mediated cell death, but only at high concentrations of palmitate (400-500 [micro]M). Similar results were observed in primary hepatocytes isolated from Chop-knockout mice. Indices of liver injury were also not reduced in Chop-knockout mice provided a methionine-choline-deficient diet. To ascertain whether ER stress was linked to palmitate-induced cell death, primary hepatocytes were incubated in the absence or presence of the chemical chaperones taurine-conjugated ursodeoxycholic acid or 4-phenylbutyric acid. The presence of either of these chemical chaperones protected liver cells from palmitate-mediated ER stress and cell death, in part, via inhibition of JNK activation. These data suggest that ER stress is linked to palmitate-mediated cell death via mechanisms that include JNK activation. lipoapoptosis; unfolded protein response; nonalcoholic fatty liver disease doi:10.1152/ajpendo.00642.2009.

Myxococcus xanthus DK1622 contains two paralogous groEL gene loci that possess both different sequences and different organizations within the genome. Deletion of either one of these two genes alone does not affect cell viability. However, deletion of both groEL genes results in cell death unless a complemented groEL1 or groEL2 gene is present. The groEL1 gene was determined to be essential for cell survival under heat shock conditions; a strain with mutant groEL2 caused cells to be more sensitive than the wild-type strain to higher temperatures. Mutants with a single deletion of either groEL1 (MXAN_4895) or groEL2 (MXAN_4467) had a growth curve similar to that of the wild-type strain DK1622 in medium containing hydrolyzed proteins as the substrate. However, when cells were cultured on medium containing either Escherichia coli cells or casein as the substrate, deletion of groEL2, but not groEL1, led to a deficiency in cell predation and macromolecular feeding. Furthermore, groEL1 was found to play an indispensable role in the development and sporulation of cells, but deletion of groEL2 had no visible effects. Our results suggest that, although alternatively required for cell viability, the products of the two groEL genes have divergent functions in the multicellular social life cycle of M. xanthus DK1622. doi:10.1128/JB.01458-09

The X S gene encodes a holin, S105, and an antiholin, S107, which differs by its Met-Lys N-terminal extension. The model for the lysis-defective character of S107 stipulates that the additional N-terminal basic residue keeps S107 from assuming the topology of S105, which is N-out, C-in, with three transmembrane domains (TMDs). Here we show that the N terminus of S105 retains its fMet residue but that the N terminus of S107 is fully deformylated. This supports the model that in S105, TMD1 inserts into the membrane very rapidly but that in S107, it is retained in the cytoplasm. Further, it reveals that, compared to S105, S107 has two extra positively charged moieties, Lys2 and the free N-terminal amino group, to hinder its penetration into an energized membrane. Moreover, an allele, [S105.sub.[DELTA]TMD1], with TMD1 deleted, was found to be defective in lysis, insensitive to membrane depolarization, and dominant to the wild-type allele, indicating that the lysis-defective, antiholin character of S107 is due to the absence of TMD1 from the bilayer rather than to its ectopic localization at the inner face of the cytoplasmic membrane. Finally, the antiholin function of the deletion protein was compromised by the substitution of early-lysis missense mutations in either the deletion protein or parental S105 but restored when both [S105.sub.[DELTA]TMD1] and holin carried the substitution. doi: 10.1128/JB.01263-09

Escherichia coli mazEF is a toxin-antitoxin gene module that mediates cell death during exponential-phase cellular growth through either reactive oxygen species (ROS)-dependent or ROS-independent pathways. Here, we found that the stationary-phase sigma factor [[sigma].sup.s] was responsible for the resistance to mazEF-mediated cell death during stationary growth phase. Deletion of rpoS, the gene encoding [[sigma].sup.s] from the bacterial chromosome, permitted mazEF-mediated cell death during stationary growth phase.

The sequential modifications of histones form the basis of the histone code that translates into either gene activation or repression. Nuclear receptors recruit a cohort of histone-modifying enzymes in response to ligand binding and regulate proliferation, differentiation, and cell death. In Drosophila melanogaster, the steroid hormone ecdysone binds its heterodimeric receptor ecdysone receptor/ultraspiracle to spatiotemporally regulate the transcription of several genes. In this study, we identify a novel cofactor, Drosophila lysine ketoglutarate reductase (dLKR)/saccharopine dehydrogenase (SDH), that is involved in ecdysone-mediated transcription, dLKR/SDH binds histones H3 and H4 and suppresses ecdysone-mediated transcription of cell death genes by inhibiting histone H3R17me2 mediated by the Drosophila arginine methyl transferase CARMER. Our data suggest that the dynamic recruitment of dLKR/SDH to ecdysone-regulated gene promoters controls the timing of hormone-induced gene expression. In the absence of dLKR/SDH, histone methylation occurs prematurely, resulting in enhanced gene activation. Consistent with these observations, the loss of dLKR/SDH in Drosophila enhances hormone-regulated gene expression, affecting the developmental timing of gene activation.

Enterococci are major contributors of hospital-acquired infections and have emerged as important reservoirs for the dissemination of antibiotic resistance traits. The ability to form biofilms on medical devices is an important aspect of pathogenesis in the hospital environment. The Enterococcusfaecalis Fsr quorum system has been shown to regulate biofilm formation through the production of gelatinase, but the mechanism has been hitherto unknown. Here we show that both gelatinase (GelE) and serine protease (SprE) contribute to biofilm formation by E. faecalis and provide clues to how the activity of these proteases governs this developmental process. Confocal imaging of biofilms suggested that [GelE.sup.-] mutants were significantly reduced in biofilm biomass compared to the parental strain, whereas the absence of SprE appeared to accelerate the progression of biofilm development. The phenotype observed in a [SprE.sup.-] mutant was linked to an observed increase in autolytic rate compared to the parental strain. Culture supernatant analysis and confocal microscopy confirmed the inability of mutants deficient in GelE to release extracellular DNA (eDNA) in planktonic and biofilm cultures, whereas cells deficient in SprE produced significantly more eDNA as a component of the biofilm matrix. DNase I treatment of E. faecalis biofilms reduced the accumulation of biofilm, implying a critical role for eDNA in biofilm development. In conclusion, our data suggest that the interplay of two secreted and coregulated proteases--GelE and SprE--is responsible for regulating autolysis and the release of high-molecular-weight eDNA, a critical component for the development of E. faecalis biofilms.

Nbp2p is a Nap1-binding protein in Saccharomyces cerevisiae identified by its interaction with Nap1 by a two-hybrid system. NBP2 encodes a novel protein consisting of 236 amino acids with a Src homology 3 (SH3) domain. We showed that NBP2 functions to promote mitotic cell growth at high temperatures and cell wall integrity. Loss of Nbp2 results in cell death at high temperatures and in sensitivity to calcofluor white. Cell death at high temperature is thought not to be due to a weakened cell wall. Additionally, we have isolated several type-2C serine threonine protein phosphatases (PTCs) as multicopy suppressors and MAP kinase-kinase (MAPKK), related to the yeast PKC MAPK pathway, as deletion suppressors of the nbp2[DELTA] mutant. Screening for deletion suppressors is a new genetic approach to identify and characterize additional proteins in the Nbp2-dependent pathway. Genetic analyses suggested that Ptc1, which interacts with Nbp2 by the two-hybrid system, acts downstream of Nbp2 and that cells lacking the function of Nbp2 prefer to lose Mkk1, but the PKC MAPK pathway itself is indispensable when Nbp2 is deleted at high temperature.

It is currently unclear whether Shigella kills its phagocytic host cells by apoptosis or necrosis. This study shows that rapid necrosis ensues in macrophage-like cell lines (U937 cells differentiated by all-trans-retinoic acid and J774 cells) infected with the Shigella flexneri strain YSH6000. The infected cells rapidly lose membrane integrity, a typical feature of necrosis, as indicated by the release of the cytoplasmic lactate dehydrogenase and the exposure of phosphatidylserine (PS) associated with the rapid uptake of propidium iodide (PI). The infected cells exhibit DNA fragmentation without nuclear condensation, and substantial involvement of either caspase-3/-7 or caspase-1 was not detected, which is also contrary to what is normally observed in apoptosis. Cytochalasin D potently inhibited Shigella-induced cell death, indicating that only internalized Shigella can cause necrosis. Osmoprotectants such as polyethylene glycols could suppress cell death, suggesting that insertion of a pore by Shigella into the host cell membrane induces the necrosis. The pore was estimated to be 2*87 [+ or -] 0*4 nm in diameter. Shigella was also found to be able to induce apoptosis but only in one of the lines tested and under specific conditions, namely U937 cells differentiated with interferon-[gamma] (U9371FN). Caspase-3/-7 but not caspase-1 activation was observed in these infected cells and the exposure of PS occurred without the uptake of PI. An avirulent Shigella strain, wild-type Shigella killed with gentamicin, and even Escherichia coli strain JM109, could also induce apoptosis in U9371FN cells, and cytochalasin D could not prevent apoptosis. It appears therefore that Shigella-induced apoptosis of U9371FN cells is unrelated to Shigella pathogenicity and does not require bacterial internalization. Thus, Shigella can induce rapid necrosis of macrophage-like cells in a virulence-related manner by forming pores in the host cell membrane while some cells can be killed through apoptosis in a virulence-independent fashion.

The genus Sphingobacterium, whose members are Gram-negative non-fermentative rods, possesses ceramides and related sphingophospholipids (SPLs) with isoheptadecasphinganine and 2-hydroxy or non-hydroxy isopentadecanoic acid. This paper reports evidence that ceramides isolated from Sphingobacterium ATCC 33861 induce endonucleolytic DNA cleavage in human myeloid leukaemia HL-60 cells in vitro, which is the primary characteristic biochemical marker for apoptosis or programmed cell death. Ceramides and SPLs also induced DNA fragmentation and caspase-3 activation, followed by changes in morphology, such as alterations in the size of nuclei and cells, and cell cycle shortening. Apoptotic activity correlated with the ceramide structure. Ceramide with a 2-hydroxy fatty acid showed stronger apoptotic activity than ceramide with a non-hydroxy fatty acid. Furthermore, the major five SPLs (ceramide phosphorylethanolamine-1 and -2, ceramide phosphorylinositol-1 and -2, and ceramide phosphorylmannose-1) showed apoptosis-inducing activity in HL-60 cells, indicating that the ceramide moiety of the SPLs plays a crucial role as the intracellular second messenger but that their hydrophilicity is less important in this regard. The hydrophilic part of SPLs may play a role in other cellular response systems. The involvement of Fas antigen was implicated in the apoptotic event since Fas antigen expression was observed after 3 or 4 h stimulation of HL-60 cells with bacterial ceramides. However, a time-course study for caspase-3 activation indicated maximal activity at 1 h after stimulation with bacterial ceramides, suggesting that two (or possibly more) mechanisms of signal transduction, Fas-dependent and Fas-independent, may be involved. Fas antigen expression and caspase-3 activation by five kinds of SPLs were observed after 3 or 4 h. These results indicate that there is a difference in the response of HL-60 cells to bacterial ceramides and SPLs.

Bacteria growing in biofilms often develop multicellular, three-dimensional structures known as microcolonies. Complex differentiation within biofilms of Pseudomonas aeruginosa occurs, leading to the creation of voids inside microcolonies and to the dispersal of cells from within these voids. However, key developmental processes regulating these events are poorly understood. A normal component of multicellular development is cell death. Here we report that a repeatable pattern of cell death and lysis occurs in biofilms of P. aeruginosa during the normal course of development. Cell death occurred with temporal and spatial organization within biofilms, inside microcolonies, when the biofilms were allowed to develop in continuous-culture flow cells. A subpopulation of viable cells was always observed in these regions. During the onset of biofilm killing and during biofilm development thereafter, a bacteriophage capable of superinfecting and lysing the P. aeruginosa parent strain was detected in the fluid effluent from the biofilm. The bacteriophage implicated in biofiim killing was closely related to the filamentous phage Pf1 and existed as a prophage within the genome of P. aeruginosa. We propose that prophage-mediated cell death is an important mechanism of differentiation inside microcolonies that facilitates dispersal of a subpopulation of surviving cells.

Mitochondrial release of cytochrome c in apoptotic cells activates caspases, which execute apoptotic cell death. However, the events themselves that culminate in caspase activation can have deleterious effects because caspase inhibitor-saved cells ultimately die in a caspase-independent manner. To determine what events may underlie this form of cell death, we examined bioenergetic changes in sympathetic neurons deprived of NGF in the presence of a broad-spectrum caspase inhibitor, boc-aspartyl-(OMe)-fluoromethylketone. Here, we report that NGF-deprived,boc-aspartyl-(OMe)-fluoromethylketone--saved neurons rely heavily on glycolysis for ATP generation and for survival. Second, the activity of F0F1 contributes to caspase-independent death, but has only a minor role in the maintenance of mitochondrial membrane potential, which is maintained primarily by electron transport. Third, permeability transition pore inhibition by cyclosporin A attenuates NGF deprivation-induced loss of mitochondrial proteins, suggesting that permeability transition pore opening may have a function in regulating the degradation of mitochondria after cytochrome c release. Identification of changes in caspase inhibitor-saved cells may provide the basis for rational strategies to augment the effectiveness of the therapeutic use of postmitochondrial interventions.

Caspase-directed apoptosis usually fragments cells, releasing nonfunctional, prothrombogenic, membrane-bound apoptotic bodies marked for rapid engulfment by macrophages. Blood platelets are functional anucleate cells generated by specialized fragmentation of their progenitors, megakaryocytes (MKs), but committed to a constitutive caspase-independent death. Constitutive formation of the proplatelet-bearing MK was recently reported to be caspase-dependent, apparently involving mitochondrial release of cytochrome c, a known pro-apoptogenic factor. We extend those studies and report that activation of caspases in MKs, either constitutively or after Fas ligation, yields platelets that are functionally responsive and evade immediate phagocytic clearance, and retain mitochondrial transmembrane potential until constitutive platelet death ensues. Furthermore, the exclusion from the platelet progeny of caspase-9 present in the progenitor accounts for failure of mitochondrial release of cytochrome c to activate caspase-3 during platelet death. Thus, progenitor cell death by apoptosis can result in birth of multiple functional anucleate daughter cells.

Steroid hormones trigger a wide variety of cell-specific responses during animal development, but the mechanisms by which these systemic signals specify either cell division, differentiation, morphogenesis or death remain uncertain. Here, we analyze the function of the steroid-regulated genes [beta]FTZ-F1, BR-C, E74A, and E93 during salivary gland programmed cell death. While mutations in the [beta]FTZ-F1, BR-C, E74A, and E93 genes prevent destruction of salivary glands, only [beta]FTZ-F1 is required for DNA fragmentation. Analyses of BR-C, E74A, and E93 loss-of-function mutants indicate that these genes regulate stage-specific transcription of the rpr, hid, ark, dronc, and crq cell death genes. Ectopic expression of [beta]FTZ-F1 is sufficient to trigger premature cell death of larval salivary glands and ectopic transcription of the rpr, dronc, and crq cell death genes that normally precedes salivary gland cell death. The E93 gene is necessary for ectopic salivary gland cell destruction, and ectopic rpr, dronc, and crq transcription, that is induced by expression of [beta]FTZ.F1. Together, these observations indicate that [beta]FTZ-F1 regulates the timing of hormone-induced cell responses, while E93 functions to specify programmed cell death. Key Words: steroid; ecdysone; programmed cell death; apoptosis; autophagy; development; metamorphosis; Drosophila.

Research has been conducted on apoptotic cell death. Results demonstrate that the null mutation in Drosophila gene for inhibitor of capsase-activated DNase has been established via P-element insertion and that CAD and DNase degrade chromosomal DNA during apoptosis independently.

Recovery from injury is usually accompanied by cell replication, in which new cells replace those irreparably damaged. After acute renal failure, normally quiescent kidney cells enter the cell cycle, which in tubule segments is accompanied by the induction of cell cycle inhibitors. We found that after acute renal failure induced by either cisplatin injection or renal ischemia, induction of the p21 cyclin-dependent kinase (cdk) inhibitor is protective. Mice lacking this gene developed more widespread kidney cell death, more severe renal failure, and had reduced survival, compared with mice with a functional p21 gene. Here, we show induction of 14-3-3cr, a regulator of G2-to-M transition, after acute renal failure. Our findings, using both in vivo and in vitro models of acute renal failure, show that this protein likely helps to coordinate cell cycle activity to maximize recovery of renal epithelial cells from injury and reduce the extent of the injury itself. Because in terminally differentiated cells, these proteins are highly expressed only after injury, we propose that cell cycle coordination by induction of these proteins could be a general model of tissue recovery from stress and injury. kidney failure; acute; p21 cyclin kinase inhibitor; cisplatin; ischemia

The events occurring early in the burn wound trigger a sequence of local and systemic responses that influence cell and tissue survival and, consequently, wound healing and recovery. Using high-density oligonucleotide arrays we identified gene expression patterns in skin samples taken from a region of injury in the burn rat model. The associated genomic events include the differential expression of genes involved in cell survival and death, cell growth regulation, cell metabolism, inflammation, and immune response. The functional gene cluster detected and their time appearance matched the time sequence known to occur in burn wound healing. gene expression profile; microarray; wound healing; skin; rat burn model

Drosophila germ cells form at the posterior pole of the embryo and migrate to the somatic gonad. Approximately 50% of the germ cells that form reach their target. The errant cells within the embryo undergo developmentally regulated cell death. Prior studies have identified some autosomal genes that regulate germ cell migration, but the genes that control germ cell death are not known. To identify X-linked genes required for germ cell migration and/or death, we performed a screen for mutations that disrupt these processes. Here we report the identification of scattershot and outsiders, two genes that regulate the programmed death of germ cells. The scattershot gene is defined by a mutation that disrupts both germ cell migration and the death of germ cells ectopic to the gonad. Maternal and zygotic expression of scattershot is required, but the migration and cell death functions can be genetically uncoupled. Zygotic expression of wild-type scattershot rescues germ cell pathfinding, but does not restore the programmed death of errant cells. The outsiders gene is required zygotically. In outsiders mutant embryos, the appropriate number of germ cells is incorporated into the gonad, but germ cells ectopic to the gonad persist.

Research demonstrates that salvadar gene promotes both cell cycle exit and cell death and this process determines the number of cells in an organism. The salvador gene is identifiable in Drosophila mutants but the human counterrpart is mutated in some cancer cell lines.

Mutations in the X-linked Plp gene lead to dysmyelinating phenotypes and oligodendrocyte cell death. Here, we exploit the X inactivation phenomenon to show that a hierarchy exists in the influence of different mutant Pip alleles on oligodendrocyte survival. We used compound heterozygote mice to study the long-term fate of oligodendrocytes expressing either the jimpy or rumpshaker allele against a background of cells expressing a Plp-null allele. Although mutant and null oligodendrocytes were generated in equal numbers, the proportion expressing the mutant allele subsequently declined, but whereas those expressing the rumpshaker allele formed a reduced but stable population, the number of jimpy cells fell progressively. The age of decline in the jimpy cells in different regions of the CNS correlated with the temporal sequence of myelination. In compound heterozygotes expressing rumpshaker and jimpy alleles, oligodendrocytes expressing the former predominated and were more abundant than when the rumpshaker and null alleles were in competition. Thus, oligodendrocyte survival is not determined solely by cell intrinsic factors, such as the conformation of the misfolded PLP, but is influenced by neighboring cells, possibly competing for cell survival factors.

We have selectively inhibited Notch1 signaling in oligodendrocyte precursors (OPCs) using the Cre/IoxP system in transgenic mice to investigate the role of Notch1 in oligodendrocyte (OL) development and differentiation. Early development of OPCs appeared normal in the spinal cord. However, at embryonic day 17.5, premature OL differentiation was observed and ectopic immature OLs were present in the gray matter. At birth, OL apoptosis was strongly increased in Notchl mutant animals. Premature OL differentiation was also observed in the cerebrum, indicating that Notch1 is required for the correct spatial and temporal regulation of OL differentiation in various regions of the central nervous system. These findings establish a widespread function of Notch1 in the late steps of mammalian OPC development in vivo.

Caspase-independent death mechanisms have been shown to execute apoptosis in many types of neuronal injury. P53 has been identified as a key regulator of neuronal cell death after acute injury such as DNA damage, ischemia, and excitotoxicity. Here, we demonstrate that p53 can induce neuronal cell death via a caspase-mediated process activated by apoptotic activating factor-1 (Apaf1) and via a delayed onset caspase-independent mechanism. In contrast to wild-type cells, Apaf1-deficient neurons exhibit delayed DNA fragmentation and only peripheral chromatin condensation. More importantly, we demonstrate that apoptosis-inducing factor (AIF) is an important factor involved in the regulation of this caspase-independent neuronal cell death. Immunofluorescence studies demonstrate that AIF is released from the mitochondria by a mechanism distinct from that of cytochrome-c in neurons undergoing p53-mediated cell death. The Bcl-2 family regulates this release of AIF and subsequent caspase-independent cell death. In addition, we show that enforced expression of AIF can induce neuronal cell death in a Bax- and caspase-independent manner. Microinjection of neutralizing antibodies against AIF significantly decreased injury-induced neuronal cell death in Apaf1-deficient neurons, indicating its importance in caspase-independent apoptosis. Taken together, our results suggest that AIF may be an important therapeutic target for the treatment of neuronal injury.

Sympathetic neurons depend on NGF binding to TrkA for their survival during vertebrate development. NGF deprivation initiates a transcription-dependent apoptotic response, which is suggested to require activation of the transcription factor c-Jun. Similarly, apoptosis can also be induced by selective activation of the p75 neurotrophin receptor. The transcriptional dependency of p75-mediated cell death has not been determined; however, c-Jun N[H.sub.2]-terminal kinase has been implicated as an essential component. Because the c-jun--null mutation is early embryonic lethal, thereby hindering a genetic analysis, we used the Cre-lox system to conditionally delete this gene. Sympathetic neurons isolated from postnatal day 1 c-jun-floxed mice were infected with an adenovirus expressing Cre recombinase or GFP and analyzed for their dependence on NGF for survival. Cre immunopositive neurons survived NGF withdrawal, whereas those expressing GFP or those uninfected underwent apoptosis within 48 h, as determined by DAPI staining. In contrast, brain-derived neurotrophic factor (BDNF) binding to p75 resulted in an equivalent level of apoptosis in neurons expressing Cre, GFP, and uninfected cells. Nevertheless, cycloheximide treatment prevented BDNF-mediated apoptosis. These results indicate that whereas c-jun is required for apoptosis in sympathetic neurons on NGF withdrawal, an alternate signaling pathway must be induced on p75 activation.

Research has been conducted on the peptides based on Bcl-2 anti-apoptotic oncoprotein. The design and synthesis of the peptides based on the BH3 domains of the Bcl-2, Bax and Bad family members and the results implicate the importance of the peptides derived from different BH3 domains.

p53 is a transcription factor that induces growth arrest or apoptosis in response to cellular stress. To identify new p53-inducible proapoptotic genes, we compared, by differential display, the expression of genes in spleen or thymus of normal and p53 nullizygote mice after [gamma]-irradiation of whole animals. We report the identification and characterization of human and mouse Scotin homologues, a novel gene directly transactivated by p53. The Scotin protein is localized to the ER and the nuclear membrane. Scotin can induce apoptosis in a caspase-dependent manner. Inhibition of endogenous Scotin expression increases resistance to p53-dependent apoptosis induced by DNA damage, suggesting that Scotin plays a role in p53-dependent apoptosis. The discovery of Scotin brings to light a role of the ER in p53-dependent apoptosis.

Research has been conducted on mammalian ATF/CREB family of transcription factors which consists of basic-region leucine zipper proteins. Results indicate that the mouse ATFx gene expression down-regulates growth factor deprivation and that ATFx is an anti-apoptotic factor.

Research has been conducted on Salmonella enterica serovar Typhimurium hemA gene. Results demonstrate that hemA-deficient cell exposure to hydrogen peroxide leads to the iron-dependent DNA damage and cell death.

The authors reviews the publications on the apoptosis protein inhibitors which block apoptosis via interactions with the cysteine proteases' caspase family members. Topics of interest include ubiquitin-proteasome mediated destruction of Drosophila inhibitors of apoptosis proteins and its role in the programmed cell death initiation in the fly.

Wee1 kinases catalyze inhibitory phosphorylation of the mitotic regulator Cdk1, preventing mitosis during S phase and delaying it in response to DNA damage or developmental signals during G2. Unlike yeast, metazoans have two distinct Wee1-like kinases, a nuclear protein (Wee1) and a cytoplasmic protein (Myt1). We have isolated the genes encoding Drosophila Wee1 and Myt1 and are using genetic approaches to dissect their functions during normal development. Overexpression of Dwee1 or Dmyt1 during eye development generates a rough adult eye phenotype. The phenotype can be modified by altering the gene dosage of known regulators of the G2/M transition, suggesting that we could use these transgenic strains in modifier screens to identify potential regulators of Wee1 and Myt1. To confirm this idea, we tested a collection of deletions for loci that can modify the eye overexpression phenotypes and identified several loci as dominant modifiers. Mutations affecting the Delta/Notch signaling pathway strongly enhance a GMR-Dmyt1 eye phenotype but do not affect a GMR-Dwee1 eye phenotype, suggesting that Myt1 is potentially a downstream target for Notch activity during eye development. We also observed interactions with p53, which suggest that Wee1 and Myt1 activity can block apoptosis.

Research has been conducted on the expanded polyglutamine causing inherited neurodegenerative disorders. The role of ASK1 in the endoplasmic reticulum stress-induced cell death and in the neuropathalogical alterations in polyglutamine diseases has been investigated and the details are reported.

The authors discuss the publications on the human neurodegenerative diseases, associated with glutamine repeats abnormal expansion. The topics of interest include polyglutamine proteotoxicity components, unfolded protein response, programmed cell death and endoplasmic reticulum stress.

Research reveals that murine lymphomas respond to cancer treatment through a senescence process controlled by p53 and p16(sup)INK4a genes as shown by poor response to chemotherapy by tumors containing mutations in the genes. Data indicate a connection between cellular senescence and treatment outcome in cancer management.

Research has been conducted on the interactions between p53 and PI3K/AKT pathways. The role of these interactions in cell death and survival determination has been determined and the results indicate that p53 regulates cell survival via PI3K/AKT prosurvival signal inhibition.

Research has been conducted on the null mouse gastric mucosa. Results indicate that this mucosa exhibits hyperplasias caused by stimulated proliferation and suppressed apoptosis in the cells.

Research has been conducted on the transcription factor Pax-3 which is expressed in the neural tube. Results demonstrate that p53 deficiency caused by the germ-line mutation or by pifithrin-alpha rescues apoptosis and the neural tube defects in the Splotch embryos.

Because we recently identified the Gaolf subunit in rat pancreatic [beta]-cells, we investigated the downstream effectors and the biological functions of this G protein in HEK-293T cells and the insulin-secreting mouse [beta]TC-3 cell line. With the use of transient transfection of HEK-293T cells with constitutively activated Gaolf(GaolfQ214L, i.e., AGaolf), together with expression vectors encoding the adenylyl cyclase (AC) isoforms (AC-I to -VIII and soluble AC), compared with cotransfections using AGas (GasR201C), we observed that AGaolf preferentially activates AC-I and -VIII, which are also expressed in [beta]-cells. Stable overexpression of wild-type or AGaolf in [beta]TC-3 cells resulted in partial attenuation of insulin secretion and biosynthesis, suggesting that chronic activation of the Gaolf-signaling pathway is associated with [beta]-cell desensitization. In agreement, transfected [beta]TC-3 cells present a decreased insulin content with respect to parental cells, whereas the proinsulin convertases PC-1 and PC-2 were unaffected. Furthermore, [beta]TC-3-AG[alpha]olf cells are resistant to serum starvation-induced apoptosis. Our findings suggest that Gaolf is involved in insulin status, cell survival, and regeneration of the insulin-secreting [beta]-cells during development and diabetes. Gaolf subunit; apoptosis; diabetes; regeneration

Research has been conducted on the anthraquinone-2,6-disulfonate (AQDS) used as an electron shuttle during extracellular electron transfer. Results indicate that AQDS enters the Shewanella oneidensis strain MR-1 and causes cell death, and that there may be functional and structural relationship between quinone-containing electron shuttles and antibiotics.

Knockout of Arabidopsis ACCELERATED-CELL-DEATH11 encoding a sphingosine transfer protein has been shown to bring on activation of programmed cell death and defense. ACD11 speeds the transfer of sphingosine, but not of glycosphingolipids, between membranes in vitro.

This review discusses the basis of tumorigenesis and drug resistance in relation to induction of apoptosis by chemotherauptic drugs, which enable the cancer cells evade apoptotic death. Research suggests that understanding this relationship paves way for better anticancer drug design and therapy.

Protein kinase C-[zeta] modulates thromboxane [A.sub.2]-mediated apoptosis in adult ventricular myocytes via Akt. Am J Physiol Heart Circ Physiol 282: H320-H327, 2002.--We hypothesized that thromboxane [A.sub.2] (Tx[A.sub.2]) receptor stimulation directly induces apoptosis in adult cardiac myocytes. To investigate this, we exposed cultured adult rat ventricular myocytes (ARVM) to a Tx[A.sub.2] mimetic [1S-[1[alpha],2[alpha](Z),3[beta](1E,3[S.sup.*]), 4[alpha]]]-7-[3-[3-hydroxy-4-(4-iodophenoxy)-1-butenyl] -7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (I-BOP) for 24 h. Stimulation with I-BOP induced apoptosis in a dose-dependent manner and was completely prevented by a Tx[A.sub.2] receptor antagonist, SQ-29548. We further investigated the role of protein kinase C (PKC) in this process. Tx[A.sub.2] stimulation resulted in membrane translocation of PKC-[zeta] but not PKC-[alpha], -[beta]II, -[delta], and -[member of] at 3 min and 1 h. The activation of PKC-[zeta] by I-BOP was confirmed using an immune complex kinase assay. Treatment of ARVM with a cell-permeable PKC-[zeta] pseudosubstrate peptide ([zeta]-PS) significantly attenuated apoptosis by I-BOP. In addition, I-BOP treatment decreased baseline Akt activity and its decrease was reversed by treatment with [zeta]-PS. The inhibition of phosphatidylinositol 3-kinase upstream of Akt by wortmannin or LY-294002 abolished the antiapoptotic effect of [zeta]-PS. Therefore, our results suggest that the activation of PKC-[zeta] modulates Tx[A.sub.2] receptor-mediated apoptosis at least, in part, through Akt activity in adult cardiac myocytes. atypical protein kinase C; eicosanoids; Akt/protein kinase B; mitogen activated protein kinases

Load-dependent induction of apoptosis in multicellular myocardial preparations. Am J Physiol Heart Circ Physiol 282: H349-H356, 2002; 10.1152/ajpheart.00024.2001.--Increased mechanical load has been proposed as an inductor of apoptosis, but it is unknown whether this can occur in the range of pre- and afterloads that prevail in the beating heart. We investigated apoptosis in cultured rabbit multicellular myocardial preparations over several days. Muscles contracted in absence of pre- and afterload (unloaded isotonic), in absence of preload but in presence of afterload (unloaded isometric), or in presence of both (loaded isometric). After up to 48 h of continuous contractions, apoptosis was assessed by TdT-mediated nick-end labeling (TUNEL) assay and DNA ladder analysis. In muscles that contracted loaded isometric, apoptosis was detected after 6-24 h. After 48 h, apoptosis was most prominent in this group, reflected by a high level of DNA ladder intensity (DLI; 27.8 [+ or -] 11.5), whereas Bcl-xL (on RNA level) was significantly downregulated, and Fas remained unchanged. In unloaded isometric preparations, apoptosis was significantly less (6.9 [+ or -] 5.9 DLI) and very similar to those contracting unloaded isotonic (6.1 [+ or -] 5.1 DLI). We conclude that load-dependent apoptosis can occur at sarcomere lengths achievable in vivo and may mainly result from increased preload. preload; afterload; calcium; trabeculae; stretch; myocyte; Bcl-xL; Fas; TdT-mediated nick-end labeling

Roles of PPAR(beta)/(delta) in keratinocyte inflammation response are discussed. Immediately after skin injury comes release of inflammatory signals. Using cultures of primary keratinocytes from wild-type and PPAR(beta)/(delta)(super.-/-) mice has been helpful in finding that such signals induce keratinocyte differentiation through influencing TNF-alpha and IFN-gamma.