151
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Züllig S, Neukomm LJ, Jovanovic M, Charette SJ, Lyssenko NN, Halleck MS, Reutelingsperger CPM, Schlegel RA, Hengartner MO. Aminophospholipid translocase TAT-1 promotes phosphatidylserine exposure during C. elegans apoptosis. Curr Biol 2007; 17:994-9. [PMID: 17540571 DOI: 10.1016/j.cub.2007.05.024] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Revised: 05/02/2007] [Accepted: 05/02/2007] [Indexed: 12/01/2022]
Abstract
Phospholipids are distributed asymmetrically across the plasma-membrane bilayer of eukaryotic cells: Phosphatidylserine (PS), phosphatidylethanolamine, and phosphoinositides are predominantly restricted to the inner leaflet, whereas phophatidylcholine and sphingolipids are enriched on the outer leaflet [1, 2]. Exposure of PS on the cell surface is a conserved feature of apoptosis and plays an important role in promoting the clearance of apoptotic cells by phagocytosis [3]. However, the molecular mechanism that drives PS exposure remains mysterious. To address this issue, we studied cell-surface changes during apoptosis in the nematode C. elegans. Here, we show that PS exposure can readily be detected on apoptotic C. elegans cells. We generated a transgenic strain expressing a GFP::Annexin V reporter to screen for genes required for this process. Although none of the known engulfment genes was required, RNAi knockdown of the putative aminophospholipid transporter gene tat-1 abrogated PS exposure on apoptotic cells. tat-1(RNAi) also reduced the efficiency of cell-corpse clearance, suggesting that PS exposure acts as an "eat-me" signal in worms. We propose that tat-1 homologs might also play an important role in PS exposure in mammals.
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Affiliation(s)
- Stephanie Züllig
- Institute of Molecular Biology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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152
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Tan FJ, Fire AZ, Hill RB. Regulation of apoptosis by C. elegans CED-9 in the absence of the C-terminal transmembrane domain. Cell Death Differ 2007; 14:1925-35. [PMID: 17703231 PMCID: PMC3047747 DOI: 10.1038/sj.cdd.4402215] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Bcl-2 proteins regulate apoptosis in organisms as diverse as mammals and nematodes. These proteins are often localized at mitochondria by a C-terminal transmembrane domain. Although the transmembrane domain and mitochondrial localization are centrally involved in specific cases of vertebrate Bcl-2 activity, the significance of this localization is not clear for all species. Studying the Caenorhabditis elegans Bcl-2 homolog CED-9, we found that the transmembrane domain was both necessary and sufficient for localization at mitochondrial outer membranes. Furthermore, we found that in our assays, ced-9 transgenes lacking the transmembrane domain, although somewhat less active than equivalent transgenes derived from wild-type ced-9, rescued embryonic lethality of ced-9(lf) animals and responded properly to upstream signals in controlling the fate of Pn.aap neurons. Both of these apoptotic activities were retained in a construct where CED-9 lacking the transmembrane domain was targeted to the cytosolic surface of the endoplasmic reticulum and derived organelles, suggesting that in wild-type animals, accumulation at mitochondria is not essential for CED-9 to either inhibit or promote apoptosis in C. elegans. Taken together, these data are consistent with a multimodal character of CED-9 action, with an ability to regulate apoptosis through interactions in the cytosol coexisting with additional evolutionarily conserved role(s) at the membrane.
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Affiliation(s)
- FJ Tan
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - AZ Fire
- Departments of Pathology and Genetics, Stanford University SOM, Stanford, CA 94305, USA
| | - RB Hill
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
- Corresponding author: RB Hill, Department of Biology, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA. Tel: + 1 410 516 6783; Fax: + 1 702 441 2490;
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153
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Schwartz HT. A protocol describing pharynx counts and a review of other assays of apoptotic cell death in the nematode worm Caenorhabditis elegans. Nat Protoc 2007; 2:705-14. [PMID: 17406633 DOI: 10.1038/nprot.2007.93] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Studies of the nematode worm Caenorhabditis elegans have provided important insights into the genetics of programmed cell death (PCD), and revealed molecular mechanisms conserved from nematodes to humans. The organism continues to offer opportunities to investigate the processes of apoptosis under very well-defined conditions and at single-cell resolution in living animals. Here, a survey of the common methods used to study the process of PCD in C. elegans is described. Detailed instructions are provided for one standard method--the counting of extra cells of the anterior pharynx--a quantitative technique that can be used to detect even very subtle alterations in the progression of apoptotic cell death.
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Affiliation(s)
- Hillel T Schwartz
- MIT Department of Biology, Howard Hughes Medical Institute, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
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154
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Li W, Baker NE. Engulfment Is Required for Cell Competition. Cell 2007; 129:1215-25. [PMID: 17574031 DOI: 10.1016/j.cell.2007.03.054] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2006] [Revised: 01/22/2007] [Accepted: 03/29/2007] [Indexed: 11/18/2022]
Abstract
Genetic mosaics that place cells in competition within tissues may model features of tissue repair and tumor development and may reveal mechanisms of growth regulation. In one example, normal cells eliminate "Minute" cells that have reduced ribosomal protein gene dose and grow at their expense, replacing the Minute cells within developing compartments. We describe genes that are required by wild-type cells to kill Minute neighbors in Drosophila. The engulfment genes draper, wasp, the phosphatidylserine receptor, mbc/dock180, and rac1 are needed in wild-type cells for the death of Minute neighbors, whose corpses are engulfed by wild-type cells. Wild-type cells can themselves be killed by cells with elevated engulfing activity. Thus engulfment genes act downstream of growth differences between cells to eliminate cells with reduced ribosomal gene dose.
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Affiliation(s)
- Wei Li
- Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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155
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Kamimura K, Mishima Y, Obata M, Endo T, Aoyagi Y, Kominami R. Lack of Bcl11b tumor suppressor results in vulnerability to DNA replication stress and damages. Oncogene 2007; 26:5840-50. [PMID: 17369851 DOI: 10.1038/sj.onc.1210388] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Bcl11b/Rit1 is involved in T-cell development and undergoes chromosomal rearrangements in human T-cell leukemias. Thymocytes of Bcl11b(-/-) newborn mice exhibit apoptosis at a certain developmental stage when thymocytes re-enter into the cell-cycle. Here, we show that Bcl11b-knockdown T-cell lines, when exposed to growth stimuli, exhibited apoptosis at the S phase with concomitant decreases in a cell-cycle inhibitor, p27 and an antiapoptotic protein, Bcl-xL, owing to transcriptional repression. This repression was a likely consequence of the impairment of Sirt1, a nicotinamide adenine dinucleotide-dependent deacetylase associating with Bcl11b. Activation of the apoptotic process cleaved the mediator protein, Claspin, and inhibited phosphorylation of cell-cycle checkpoint kinase 1 (Chk1) that plays a central role in sensing and responding to incomplete replication. Bcl11b(-/-) thymocytes also failed to phosphorylate Chk1 when UV irradiated. These results implicate Bcl11b in the remedy for DNA replication stress and maintenance of genomic integrity.
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Affiliation(s)
- K Kamimura
- Department of Molecular Genetics, Niigata University Graduate School of Medical and Dental Sciences, Asahimachi 1-757, Niigata 951-8510, Japan
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156
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Huang Y, Lee C, Borgström P, Gjerset RA. Macrophage-mediated Bystander Effect Triggered by Tumor Cell Apoptosis. Mol Ther 2007; 15:524-33. [PMID: 17228313 DOI: 10.1038/sj.mt.6300080] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Restoration of apoptosis is an important therapeutic strategy for cancer, but bystander effects may be crucial to treatment success. We examined the involvement of bystander effects in the outcome of pro-apoptotic treatments and investigated the role of macrophages. Using a murine N202 breast cancer chamber model and intravital microscopy, we observed bystander apoptosis in vivo in mixed spheroids consisting of bystander N202 cells plus modified N202 cells overexpressing the p14ARF N-terminal region, which promotes p53-mediated apoptosis. The effect was not observed in cocultures in vitro, and could not be transferred through conditioned medium from modified N202 cells. However, if macrophages were also included in the N202 co-cultures, bystander apoptosis was restored, and correlated with elevated surface expression of phosphatidyl serine, a macrophage recognition molecule, on the modified N202 cells. Bystander killing was not observed in cocultures of N202 cells plus macrophages plus cisplatin-treated or 5-fluorouracil-treated N202 cells, where apoptosis induction in the target cell population was inefficient, suggesting that specific activation of macrophages by apoptotic tumor cells was required. The results suggest that pro-apoptotic therapies benefit both from the intrinsic vulnerability of cancer cells to apoptosis and from an innate immune response that amplifies the therapeutic effect.
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Affiliation(s)
- Yinghui Huang
- Sidney Kimmel Cancer Center, San Diego, California, USA
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157
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Buttner EA, Gil-Krzewska AJ, Rajpurohit AK, Hunter CP. Progression from mitotic catastrophe to germ cell death in Caenorhabditis elegans lis-1 mutants requires the spindle checkpoint. Dev Biol 2007; 305:397-410. [PMID: 17376425 PMCID: PMC2000799 DOI: 10.1016/j.ydbio.2007.02.024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Revised: 12/23/2006] [Accepted: 02/16/2007] [Indexed: 01/31/2023]
Abstract
Deletion of the lissencephaly disease gene LIS-1 in humans causes an extreme disorganization of the brain associated with significant reduction in cortical neurons. Here we show that deletion or RNA interference (RNAi) of Caenorhabditis elegans lis-1 results in a reduction in germline nuclei and causes a variety of cellular, developmental, and neurological defects throughout development. Our analysis of the germline defects suggests that the reduction in nuclei number stems from dysfunctional mitotic spindles resulting in cell cycle arrest and eventually programmed cell death (apoptosis). Deletion of the spindle checkpoint gene mdf-1 blocks lis-1(lf)-induced cell cycle arrest and germline apoptosis, placing the spindle checkpoint pathway upstream of the programmed cell death pathway. These results suggest that apoptosis may contribute to the cell-sparse pathology of lissencephaly.
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Affiliation(s)
- Edgar A Buttner
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138-2020, USA.
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158
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Logan MA, Freeman MR. The scoop on the fly brain: glial engulfment functions in Drosophila. NEURON GLIA BIOLOGY 2007; 3:63-74. [PMID: 18172512 PMCID: PMC2171361 DOI: 10.1017/s1740925x07000646] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Glial cells provide support and protection for neurons in the embryonic and adult brain, mediated in part through the phagocytic activity of glia. Glial cells engulf apoptotic cells and pruned neurites from the developing nervous system, and also clear degenerating neuronal debris from the adult brain after neural trauma. Studies indicate that Drosophila melanogaster is an ideal model system to elucidate the mechanisms of engulfment by glia. The recent studies reviewed here show that many features of glial engulfment are conserved across species and argue that work in Drosophila will provide valuable cellular and molecular insight into glial engulfment activity in mammals.
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Affiliation(s)
- Mary A Logan
- University of Massachusetts Medical School, Department of Neurobiology 770P, 364 Plantation Street, Worcester, MA 01605, USA.
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159
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Reddien PW, Andersen EC, Huang MC, Horvitz HR. DPL-1 DP, LIN-35 Rb and EFL-1 E2F act with the MCD-1 zinc-finger protein to promote programmed cell death in Caenorhabditis elegans. Genetics 2007; 175:1719-33. [PMID: 17237514 PMCID: PMC1855110 DOI: 10.1534/genetics.106.068148] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The genes egl-1, ced-9, ced-4, and ced-3 play major roles in programmed cell death in Caenorhabditis elegans. To identify genes that have more subtle activities, we sought mutations that confer strong cell-death defects in a genetically sensitized mutant background. Specifically, we screened for mutations that enhance the cell-death defects caused by a partial loss-of-function allele of the ced-3 caspase gene. We identified mutations in two genes not previously known to affect cell death, dpl-1 and mcd-1 (modifier of cell death). dpl-1 encodes the C. elegans homolog of DP, the human E2F-heterodimerization partner. By testing genes known to interact with dpl-1, we identified roles in cell death for four additional genes: efl-1 E2F, lin-35 Rb, lin-37 Mip40, and lin-52 dLin52. mcd-1 encodes a novel protein that contains one zinc finger and that is synthetically required with lin-35 Rb for animal viability. dpl-1 and mcd-1 act with efl-1 E2F and lin-35 Rb to promote programmed cell death and do so by regulating the killing process rather than by affecting the decision between survival and death. We propose that the DPL-1 DP, MCD-1 zinc finger, EFL-1 E2F, LIN-35 Rb, LIN-37 Mip40, and LIN-52 dLin52 proteins act together in transcriptional regulation to promote programmed cell death.
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Affiliation(s)
- Peter W Reddien
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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160
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Krysko DV, D'Herde K, Vandenabeele P. Clearance of apoptotic and necrotic cells and its immunological consequences. Apoptosis 2006; 11:1709-26. [PMID: 16951923 DOI: 10.1007/s10495-006-9527-8] [Citation(s) in RCA: 237] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The ultimate and most favorable fate of almost all dying cells is engulfment by neighboring or specialized cells. Efficient clearance of cells undergoing apoptotic death is crucial for normal tissue homeostasis and for the modulation of immune responses. Engulfment of apoptotic cells is finely regulated by a highly redundant system of receptors and bridging molecules on phagocytic cells that detect molecules specific for dying cells. Recognition of necrotic cells by phagocytes is less well understood than recognition of apoptotic cells, but an increasing number of recent studies, which are discussed here, are highlighting its importance. New observations indicate that the interaction of macrophages with dying cells initiates internalization of the apoptotic or necrotic targets, and that internalization can be preceded by "zipper"-like and macropinocytotic mechanisms, respectively. We emphasize that clearance of dying cells is an important fundamental process serving multiple functions in the regulation of normal tissue turnover and homeostasis, and is not just simple anti- or pro-inflammatory responses. Here we review recent findings on genetic pathways participating in apoptotic cell clearance, mechanisms of internalization, and molecules involved in engulfment of apoptotic versus necrotic cells, as well as their immunological consequences and relationships to disease pathogenesis.
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Affiliation(s)
- Dmitri V Krysko
- Department for Molecular Biomedical Research, Molecular Signaling and Cell Death Unit, VIB-Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
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161
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Awasaki T, Tatsumi R, Takahashi K, Arai K, Nakanishi Y, Ueda R, Ito K. Essential role of the apoptotic cell engulfment genes draper and ced-6 in programmed axon pruning during Drosophila metamorphosis. Neuron 2006; 50:855-67. [PMID: 16772168 DOI: 10.1016/j.neuron.2006.04.027] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Revised: 01/29/2006] [Accepted: 04/14/2006] [Indexed: 11/16/2022]
Abstract
Axon pruning is a common phenomenon in neural circuit development. Previous studies demonstrate that the engulfing action of glial cells is essential in this process. The underlying molecular mechanisms, however, remain unknown. We show that draper (drpr) and ced-6, which are essential for the clearance of apoptotic cells in C. elegans, function in the glial engulfment of larval axons during Drosophila metamorphosis. The drpr mutation and glia-specific knockdown of drpr and ced-6 by RNA interference suppress glial engulfment, resulting in the inhibition of axon pruning. drpr and ced-6 interact genetically in the glial action. Disruption of the microtubule cytoskeleton in the axons to be pruned occurs via ecdysone signaling, independent of glial engulfment. These findings suggest that glial cells engulf degenerating axons through drpr and ced-6. We propose that apoptotic cells and degenerating axons of living neurons are removed by a similar molecular mechanism.
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Affiliation(s)
- Takeshi Awasaki
- Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
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162
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Abstract
Engulfment of dying cells plays an important role during animal development and homeostasis, and several proteins involved in this process are known. However, the cell biology underlying phagocyte arm extension and cell corpse degradation is not well understood. A study published in this issue of Developmental Cell (Yu et al., 2006) now demonstrates an important role for the GTPase dynamin in these events.
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Affiliation(s)
- Shai Shaham
- The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
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163
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Vohra BPS, Groshong JS, Zayas R, Wollmann RL, Gomez CM. Activation of apoptotic pathways at muscle fiber synapses is circumscribed and reversible in a slow-channel syndrome model. Neurobiol Dis 2006; 23:462-70. [PMID: 16815027 DOI: 10.1016/j.nbd.2006.04.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2006] [Revised: 03/30/2006] [Accepted: 04/05/2006] [Indexed: 10/24/2022] Open
Abstract
In the slow-channel syndrome (SCS) mutant acetylcholine receptors elicit calcium overload and myonuclear degeneration at the neuromuscular junction (NMJ), without muscle fiber death. Activated caspases are present at SCS motor endplates. We hypothesized that SCS represents a limited form of apoptosis. We found condensed chromatin and occasional single-strand DNA nicks in degenerating synaptic nuclei. Cleaved forms of caspases-3 and -9 were present in mouse SCS muscle homogenates and were specifically localized to NMJs. Finally, interruption of cholinergic activity by axotomy markedly reduced NMJ caspase activity and improved the morphological features of apoptosis at NMJs. These results demonstrate that in SCS processes leading to apoptosis may remain compartmentalized and reversible. Use of cysteine protease inhibitors may aid in treatment of this and other dystrophic muscle and excitotoxic disorders. Identification of extrasynaptic factors that prevent the spread of apoptosis in SCS muscle fibers may aid in developing treatments for neurological disorders characterized by excitotoxicity or apoptosis.
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Affiliation(s)
- Bhupinder P S Vohra
- Washington University School of Medicine, Department of Pediatrics, St. Louis, MO 63110, USA
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164
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Abstract
A wide array of recurrent, non-random chromosomal translocations are associated with hematologic malignancies; experimental models have clearly demonstrated that many of these translocations are causal events during malignant transformation. Translocations involving the MLL gene are among the most common of these non-random translocations. Leukemias with MLL translocations have been the topic of intense interest because of the unusual, biphenotypic immunophenotype of these leukemias, because of the unique clinical presentation of some MLL translocations (infant leukemia and therapy-related leukemia), and because of the large number of different chromosomal loci that partner with MLL in these translocations. This review is focused on the potential mechanisms that lead to MLL translocations, and will discuss aberrant VDJ recombination, Alu-mediated recombination, non-homologous end joining, as well as the effect of DNA topoisomerase II poisons and chromatin structure.
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Affiliation(s)
- Peter D Aplan
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, National Naval Medical Center, Bldg. 8 Rm. 5101, 8901 Rockville Pike, Bethesda, MD 20889, USA.
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165
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Kokel D, Li Y, Qin J, Xue D. The nongenotoxic carcinogens naphthalene and para-dichlorobenzene suppress apoptosis in Caenorhabditis elegans. Nat Chem Biol 2006; 2:338-45. [PMID: 16699520 DOI: 10.1038/nchembio791] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2006] [Accepted: 04/13/2006] [Indexed: 11/09/2022]
Abstract
Naphthalene (1) and para-dichlorobenzene (PDCB, 2), which are widely used as moth repellents and air fresheners, cause cancer in rodents and are potential human carcinogens. However, their mechanisms of action remain unclear. Here we describe a novel method for delivering and screening hydrophobic chemicals in C. elegans and apply this technique to investigate the ways in which naphthalene and PDCB may promote tumorigenesis in mammals. We show that naphthalene and PDCB inhibit apoptosis in C. elegans, a result that suggests a cellular mechanism by which these chemicals may promote the survival and proliferation of latent tumor cells. In addition, we find that a naphthalene metabolite directly inactivates caspases by oxidizing the active site cysteine residue; this suggests a molecular mechanism by which these chemicals suppress apoptosis. Naphthalene and PDCB are the first small-molecule apoptosis inhibitors identified in C. elegans. The power of C. elegans molecular genetics, in combination with the possibility of carrying out large-scale chemical screens in this organism, makes C. elegans an attractive and economic animal model for both toxicological studies and drug screens.
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Affiliation(s)
- David Kokel
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309-0347, USA
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166
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Májai G, Petrovski G, Fésüs L. Inflammation and the apopto-phagocytic system. Immunol Lett 2006; 104:94-101. [PMID: 16378644 DOI: 10.1016/j.imlet.2005.11.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 11/16/2005] [Accepted: 11/17/2005] [Indexed: 11/30/2022]
Abstract
Although under normal conditions many cells die daily mainly by apoptosis in human tissues, inflammation does not occur. The redundant function of a relatively large number of molecules are available to recognize changes occurring on the surface of apoptotic cells, to opsonize the dead cells and to engulf the apoptotic cells previously opsonized or not. Several components of the innate immune system are utilized in this process, mainly soluble factors which bind to the distinct molecular pattern of apoptotic cells. These cells, unlike necrotic ones, do not induce the expression of inflammatory cytokines in phagocytic cells, they can even inhibit such a response and engage an active signaling process to elicit a direct anti-inflammatory effect. The molecular details of these signaling processes have not been clarified yet. Both professional and "amateur" cells can engulf apoptotic cells and mediate an anti-inflammatory action. Disturbance of these processes have significant roles in development of autoimmune diseases and highly malignant tumors.
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Affiliation(s)
- Gyöngyike Májai
- Department of Biochemistry and Molecular Biology, Research Center for Molecular Medicine, Signalling and Apoptosis Research Group of the Hungarian Academy of Sciences, Faculty of Medicine, Medical and Health Science Center, University of Debrecen, Hungary
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167
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Lettre G, Hengartner MO. Developmental apoptosis in C. elegans: a complex CEDnario. Nat Rev Mol Cell Biol 2006; 7:97-108. [PMID: 16493416 DOI: 10.1038/nrm1836] [Citation(s) in RCA: 217] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Apoptosis, an evolutionarily conserved programme of cellular self-destruction, is essential for the development and survival of most multicellular animals. It is required to ensure functional organ architecture and to maintain tissue homeostasis. During development of the simple nematode Caenorhabditis elegans, apoptosis claims over 10% of the somatic cells that are generated - these cells were healthy but unnecessary. Exciting insights into the regulation and execution of apoptosis in C. elegans have recently been made. These new findings will undoubtedly influence our perception of developmental apoptosis in more complex species, including humans.
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Affiliation(s)
- Guillaume Lettre
- Division of Genetics, Children's Hospital, 300 Longwood Avenue, Boston, Massachusetts 02115, USA
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168
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Mahadevan D, Spier C, Della Croce K, Miller S, George B, Riley C, Warner S, Grogan TM, Miller TP. Transcript profiling in peripheral T-cell lymphoma, not otherwise specified, and diffuse large B-cell lymphoma identifies distinct tumor profile signatures. Mol Cancer Ther 2006; 4:1867-79. [PMID: 16373702 DOI: 10.1158/1535-7163.mct-05-0146] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To glean biological differences and similarities of peripheral T-cell lymphoma-not otherwise specified [PTCL-NOS] to diffuse large B-cell lymphoma (DLBCL), a transcriptosome analysis was done on five PTCL-NOS and four DLBCL patients and validated by quantitative real-time reverse transcription-PCR on 10 selected genes. Normal peripheral blood T cells, peripheral blood B cells, and lymph node were used as controls. The resultant gene expression profile delineated distinct "tumor profile signatures" for PTCL-NOS and DLBCL. Several highly overexpressed genes in both PTCL-NOS and DLBCL involve the immune network, stroma, angiogenesis, and cell survival cascades that make important contributions to lymphomagenesis. Inflammatory chemokines and their receptors likely play a central role in these complex interrelated pathways: CCL2 and CXCR4 in PTCL-NOS and CCL5 and CCR1 in DLBCL. Highly overexpressed oncogenes unique to PTCL-NOS are SPI1, STK6, alpha-PDGFR, and SH2D1A, whereas in DLBCL they are PIM1, PIM2, LYN, BCL2A1, and RAB13. Oncogenes common to both lymphomas are MAFB, MET, NF-kappaB2, LCK, and LYN. Several tumor suppressors are also down-regulated (TPTE, MGC154, PTCH, ST5, and SUI1). This study illustrates the relevance of tumor-stroma immune trafficking and identified potential novel prognostic markers and targets for therapeutic intervention.
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MESH Headings
- Base Sequence
- DNA Primers
- Gene Expression Profiling
- Humans
- Immunohistochemistry
- Lymphoma, B-Cell/genetics
- Lymphoma, B-Cell/pathology
- Lymphoma, Large B-Cell, Diffuse/genetics
- Lymphoma, Large B-Cell, Diffuse/pathology
- Lymphoma, Non-Hodgkin/genetics
- Lymphoma, Non-Hodgkin/pathology
- Lymphoma, T-Cell/genetics
- Lymphoma, T-Cell/pathology
- Oligonucleotide Array Sequence Analysis
- Oncogenes
- RNA, Messenger/genetics
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
- Daruka Mahadevan
- Department of Medicine, Arizona Cancer Center, University of Arizona, 1515 North Campbell Avenue, Tucson, AZ 85724, USA.
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169
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Kim YS, Kim SS, Cho JJ, Choi DH, Hwang O, Shin DH, Chun HS, Beal MF, Joh TH. Matrix metalloproteinase-3: a novel signaling proteinase from apoptotic neuronal cells that activates microglia. J Neurosci 2006; 25:3701-11. [PMID: 15814801 PMCID: PMC6725382 DOI: 10.1523/jneurosci.4346-04.2005] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Microglial activation and inflammation are associated with progressive neuronal apoptosis in neurodegenerative human brain disorders. We sought to investigate molecular signaling mechanisms that govern activation of microglia in apoptotic neuronal degeneration. We report here that the active form of matrix metalloproteinase-3 (MMP-3) was released into the serum-deprived media (SDM) of PC12 cells and other media of apoptotic neuronal cells within 2-6 h of treatment of the cells, and SDM and catalytic domain of recombinant MMP-3 (cMMP-3) activated microglia in primary microglia cultures as well as BV2 cells, a mouse microglia cell line. Both SDM and cMMP-3 induced generation of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), IL-1beta, and interleukin-1 receptor antagonist but not IL-12 and inducible nitric oxide synthase, which are readily induced by lipopolysaccharide, in microglia, suggesting that there is a characteristic pattern of microglial cytokine induction by apoptotic neurons. Neither glial cell line-derived neurotrophic factor nor anti-inflammatory cytokines, such as IL-10 and transforming growth factor-beta1, were induced. SDM and cMMP-3 extensively released TNF-alpha from microglia and activated the nuclear factor-kappaB pathway, and these microglial responses were totally abolished by preincubation with an MMP-3 inhibitor, NNGH [N-isobutyl-N-(4-methoxyphenylsulfonyl)-glycylhydroxamic acid]. MMP-3-mediated microglial activation mostly depended on ERK (extracellular signal-regulated kinase) phosphorylation but not much on either JNK (c-Jun N-terminal protein kinase) or p38 activation. Conditioned medium of SDM- or cMMP-3-activated BV2 cells caused apoptosis of PC12 cells. These results strongly suggest that the distinctive signal of neuronal apoptosis is the release of active form of MMP-3 that activates microglia and subsequently exacerbates neuronal degeneration. Therefore, the release of MMP-3 from apoptotic neurons may play a major role in degenerative human brain disorders, such as Parkinson's disease.
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Affiliation(s)
- Yoon Seong Kim
- Burke Medical Research Institute, Weill Medical College and Graduate School of Medical Sciences of Cornell University, White Plains, New York 10605, USA
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170
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Freeman MR. Sculpting the nervous system: glial control of neuronal development. Curr Opin Neurobiol 2006; 16:119-25. [PMID: 16387489 DOI: 10.1016/j.conb.2005.12.004] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Accepted: 12/16/2005] [Indexed: 11/26/2022]
Abstract
Glial cells are not passive spectators during nervous system assembly, rather they are active participants that exert significant control over neuronal development. Well-established roles for glia in shaping the developing nervous system include providing trophic support to neurons, modulating axon pathfinding, and driving nerve fasciculation. Exciting recent studies have revealed additional ways in which glial cells also modulate neurodevelopment. Glial cells regulate the number of neurons at early developmental stages by dynamically influencing neural precursor divisions, and at later stages by promoting neuronal cell death through engulfment. Glia also participate in the fine sculpting of neuronal connections by pruning excess axonal projections, shaping dendritic spines, and secreting multiple factors that promote synapse formation and functional maturation. These recent insights provide further compelling evidence that glial cells, through their diverse cellular actions, are essential contributors to the construction of a functionally mature nervous system.
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Affiliation(s)
- Marc R Freeman
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605-2324, USA.
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171
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Duffield JS, Tipping PG, Kipari T, Cailhier JF, Clay S, Lang R, Bonventre JV, Hughes J. Conditional ablation of macrophages halts progression of crescentic glomerulonephritis. THE AMERICAN JOURNAL OF PATHOLOGY 2006; 167:1207-19. [PMID: 16251406 PMCID: PMC1603796 DOI: 10.1016/s0002-9440(10)61209-6] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The presence of macrophages in inflamed glomeruli of rat kidney correlates with proliferation and apoptosis of resident glomerular mesangial cells. We assessed the contribution of inflammatory macrophages to progressive renal injury in murine crescentic glomerulonephritis (GN). Using a novel transgenic mouse (CD11b-DTR) in which tissue macrophages can be specifically and selectively ablated by minute injections of diphtheria toxin, we depleted renal inflammatory macrophages through days 15 and 20 of progressive crescentic GN. Macrophage depletion reduced the number of glomerular crescents, improved renal function, and reduced proteinuria. Morphometric analysis of renal tubules and interstitium revealed a marked attenuation of tubular injury that was associated with reduced proliferation and apoptosis of tubular cells. The population of interstitial myofibroblasts decreased after macrophage depletion and interstitial fibrosis also decreased. In the presence of macrophages, interstitial myofibroblasts exhibited increased levels of both proliferation and apoptosis, suggesting that macrophages act to support a population of renal myofibroblasts in a high turnover state and in matrix deposition. Finally, deletion of macrophages reduced CD4 T cells in the diseased kidney. This study demonstrates that macrophages are key effectors of disease progression in crescentic GN, acting to regulate parenchymal cell populations by modulating both cell proliferation and apoptosis.
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Affiliation(s)
- Jeremy S Duffield
- Medical Research Council Centre for Inflammation Research Medical School, University of Edinburgh, UK, and the Renal Division, Brigham & Women's Hospital, Boston, MA 02115, USA.
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172
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Yan B, Wang H, Peng Y, Hu Y, Wang H, Zhang X, Chen Q, Bedford JS, Dewhirst MW, Li CY. A unique role of the DNA fragmentation factor in maintaining genomic stability. Proc Natl Acad Sci U S A 2006; 103:1504-9. [PMID: 16432220 PMCID: PMC1360538 DOI: 10.1073/pnas.0507779103] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
DNA fragmentation is a hallmark of apoptosis (programmed cell death). However, the biological function of apoptotic DNA fragmentation remains unclear. Here, we show that DNA fragmentation factor plays an important role for maintaining genomic stability. Inhibition or loss of the DNA fragmentation factor (DFF)/caspase-activated DNase (CAD), whose nuclease activity is responsible for digesting genomic DNA during apoptosis, led to significant increases in spontaneous or induced gene mutations, gene amplifications, and chromosomal instability in primary mouse cells and transformed human cell lines. The mechanism underlying genetic instability in DFF/CAD-deficient cells, at least in part, involves a small but significant elevation in the survival of cells exposed to ionizing radiation, suggesting that apoptotic DNA fragmentation factor contributes to genomic stability by ensuring the removal of cells that have suffered DNA damage. In support of this hypothesis are the observations of increased cellular transformation of mouse embryonic cells from the DFF/CAD-null mice and significantly enhanced susceptibility to radiation-induced carcinogenesis in these mice. These data, in combination with published reports on the existence of tumor-specific gene mutations/deletions in the DFF/CAD genes in human cancer samples, suggest that apoptotic DNA fragmentation factor is required for the maintenance of genetic stability and may play a role in tumor suppression.
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Affiliation(s)
- Bin Yan
- Departments of Radiation Oncology and Pathology, Duke University Medical Center, Durham, NC 27710, USA
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173
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Proskuryakov SY, Gabai VL, Konoplyannikov AG, Zamulaeva IA, Kolesnikova AI. Immunology of Apoptosis and Necrosis. BIOCHEMISTRY (MOSCOW) 2005; 70:1310-20. [PMID: 16417452 DOI: 10.1007/s10541-005-0263-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
A complex of reactions regulating the number of cells in organs and tissues under normal and pathologic conditions is one of the most important systems of multicellular organisms. In this system, which controls both cell proliferation and clearance, clearance has been given special attention during the last three decades. Some stages of the clearance are known (the choice of "unwanted" cells, their destruction not affecting the surrounding tissue, and, finally, removal of the corpses), and undeniable progress has been achieved in the understanding of the second stage mechanisms, whereas mechanisms of elimination per se of cells or their fragments still continue to be terra incognita. The clearance of such cells is mainly determined by different components of natural and adaptive immunity: phagocytes, complement, opsonins, antigen-presenting cells, etc. Recently specific "danger signals", such as hydrolases, DNA, heat shock proteins, and other potential immunogens released by cells during their elimination have been discovered. Entering the extracellular space, these signals induce inflammation and injury of the surrounding tissues, i.e., autoimmune reactions. Heat shock proteins, in addition to chaperon activity, act as signaling, costimulating, and antigen-carrying molecules in the interactions of dying cells and the immune system.
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Affiliation(s)
- S Ya Proskuryakov
- Medical Radiological Research Center, Russian Academy of Medical Sciences, Obninsk, 249036, Russia.
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174
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Abstract
Apoptosis is a highly regulated process of cell deletion and plays a fundamental role in the maintenance of tissue homeostasis in the adult organism. Numerous studies in recent years have revealed that apoptosis is a constitutive suicide programme expressed in most, if not all cells, and can be triggered by a variety of extrinsic and intrinsic signals. Many human diseases can be attributed directly or indirectly to a derangement of apoptosis, resulting in either cell accumulation, in which cell eradication or cell turnover is impaired, or cell loss, in which the apoptotic programme is inadvertently triggered. In addition, defective macrophage engulfment and degradation of cell corpses may also contribute to a dysregulation of tissue homeostasis. An increased understanding of the signalling pathways that govern the execution of apoptosis and the subsequent clearance of dying cells may thus yield novel targets for therapeutic intervention in a wide range of human maladies.
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Affiliation(s)
- B Fadeel
- Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
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175
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Yoo AS, Greenwald I. LIN-12/Notch activation leads to microRNA-mediated down-regulation of Vav in C. elegans. Science 2005; 310:1330-3. [PMID: 16239437 PMCID: PMC3010395 DOI: 10.1126/science.1119481] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Cell-cell interactions and cross-talk between signaling pathways specify Caenorhabditis elegans vulval precursor cells (VPCs) to adopt a spatial pattern: a central "1 degrees " VPC, in which epidermal growth factor receptor (EGFR)-mitogen-activated protein kinase (MAPK) activity is high and LIN-12/Notch activity is low, flanked by two "2 degrees " VPCs, in which LIN-12/Notch activity is high and EGFR-MAPK activity is low. Here, we identify a microRNA gene, mir-61, as a direct transcriptional target of LIN-12 and show that expression of mir-61 promotes the 2 degrees fate. We also identify vav-1, the ortholog of the Vav oncogene, as a target of mir-61, and show that down-regulation of VAV-1 promotes lin-12 activity in specifying the 2 degrees fate. Our results suggest that lin-12, mir-61, and vav-1 form a feedback loop that helps maximize lin-12 activity in the presumptive 2 degrees VPCs.
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Affiliation(s)
- Andrew S. Yoo
- Integrated Program in Cellular, Molecular, and Biophysical Studies, Howard Hughes Medical Institute, Columbia University College of Physicians and Surgeons, 701 West 168th Street, Room 720, New York, NY 10032, USA
| | - Iva Greenwald
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University College of Physicians and Surgeons, 701 West 168th Street, Room 720, New York, NY 10032, USA
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176
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Aplan PD. Causes of oncogenic chromosomal translocation. Trends Genet 2005; 22:46-55. [PMID: 16257470 PMCID: PMC1762911 DOI: 10.1016/j.tig.2005.10.002] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 08/16/2005] [Accepted: 10/10/2005] [Indexed: 11/21/2022]
Abstract
Non-random chromosomal translocations are frequently associated with a variety of cancers, particularly hematologic malignancies and childhood sarcomas. In addition to their diagnostic utility, chromosomal translocations are increasingly being used in the clinic to guide therapeutic decisions. However, the mechanisms that cause these translocations remain poorly understood. Illegitimate V(D)J recombination, class switch recombination, homologous recombination, non-homologous end-joining and genome fragile sites all have potential roles in the production of non-random chromosomal translocations. In addition, mutations in DNA-repair pathways have been implicated in the production of chromosomal translocations in humans, mice and yeast. Although initially surprising, the identification of these same oncogenic chromosomal translocations in peripheral blood from healthy individuals strongly suggests that the translocation is not sufficient to induce malignant transformation, and that complementary mutations are required to produce a frank malignancy.
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Affiliation(s)
- Peter D Aplan
- Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 8901 Wisconsin Ave, Bethesda, Maryland, MD 20889-5105, USA.
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177
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Lobov IB, Rao S, Carroll TJ, Vallance JE, Ito M, Ondr JK, Kurup S, Glass DA, Patel MS, Shu W, Morrisey EE, McMahon AP, Karsenty G, Lang RA. WNT7b mediates macrophage-induced programmed cell death in patterning of the vasculature. Nature 2005; 437:417-21. [PMID: 16163358 PMCID: PMC4259146 DOI: 10.1038/nature03928] [Citation(s) in RCA: 316] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Accepted: 06/10/2005] [Indexed: 12/26/2022]
Abstract
Macrophages have a critical role in inflammatory and immune responses through their ability to recognize and engulf apoptotic cells. Here we show that macrophages initiate a cell-death programme in target cells by activating the canonical WNT pathway. We show in mice that macrophage WNT7b is a short-range paracrine signal required for WNT-pathway responses and programmed cell death in the vascular endothelial cells of the temporary hyaloid vessels of the developing eye. These findings indicate that macrophages can use WNT ligands to influence cell-fate decisions--including cell death--in adjacent cells, and raise the possibility that they do so in many different cellular contexts.
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Affiliation(s)
- Ivan B Lobov
- Division of Developmental Biology, The Children's Hospital Research Foundation and Department of Ophthalmology, University of Cincinnati, Cincinnati, Ohio 45229, USA
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178
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Williams DW, Truman JW. Cellular mechanisms of dendrite pruning in Drosophila: insights from in vivo time-lapse of remodeling dendritic arborizing sensory neurons. Development 2005; 132:3631-42. [PMID: 16033801 DOI: 10.1242/dev.01928] [Citation(s) in RCA: 173] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Regressive events that refine exuberant or inaccurate connections are critical in neuronal development. We used multi-photon, time-lapse imaging to examine how dendrites of Drosophila dendritic arborizing (da) sensory neurons are eliminated during early metamorphosis, and how intrinsic and extrinsic cellular mechanisms control this deconstruction. Removal of the larval dendritic arbor involves two mechanisms: local degeneration and branch retraction. In local degeneration, major branch severing events entail focal disruption of the microtubule cytoskeleton, followed by thinning of the disrupted region, severing and fragmentation. Retraction was observed at distal tips of branches and in proximal stumps after severing events. The pruning program of da neuron dendrites is steroid induced; cell-autonomous dominant-negative inhibition of steroid action blocks local degeneration,although retraction events still occur. Our data suggest that steroid-induced changes in the epidermis may contribute to dendritic retraction. Finally, we find that phagocytic blood cells not only engulf neuronal debris but also attack and sever intact branches that show signs of destabilization.
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Affiliation(s)
- Darren W Williams
- Department of Biology, University of Washington, Seattle, WA 98195, USA.
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179
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Sha K, Fire A. Imprinting capacity of gamete lineages in Caenorhabditis elegans. Genetics 2005; 170:1633-52. [PMID: 15944356 PMCID: PMC1449763 DOI: 10.1534/genetics.104.040303] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2004] [Accepted: 04/20/2005] [Indexed: 01/05/2023] Open
Abstract
We have observed a gamete-of-origin imprinting effect in C. elegans using a set of GFP reporter transgenes. From a single progenitor line carrying an extrachromosomal unc-54::gfp transgene array, we generated three independent autosomal integrations of the unc-54::gfp transgene. The progenitor line, two of its three integrated derivatives, and a nonrelated unc-119:gfp transgene exhibit an imprinting effect: single-generation transmission of these transgenes through the male germline results in approximately 1.5- to 2.0-fold greater expression than transmission through the female germline. There is a detectable resetting of the imprint after passage through the opposite germline for a single generation, indicating that the imprinted status of the transgenes is reversible. In cases where the transgene is maintained in either the oocyte lineage or sperm lineage for multiple, consecutive generations, a full reset requires passage through the opposite germline for several generations. Taken together, our results indicate that C. elegans has the ability to imprint chromosomes and that differences in the cell and/or molecular biology of oogenesis and spermatogenesis are manifest in an imprint that can persist in both somatic and germline gene expression for multiple generations.
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Affiliation(s)
- Ky Sha
- Carnegie Institution of Washington, Department of Embryology, Baltimore, Maryland 21210, USA
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180
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Schwab JM, Schluesener HJ. Microglia rules: insights into microglial-neuronal signaling. Cell Death Differ 2005; 11:1245-6. [PMID: 15359293 DOI: 10.1038/sj.cdd.4401487] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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181
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Abstract
Phagocytosis requires receptor-mediated recognition of particles, usually in the guise of infectious agents and apoptotic cells. Phagosomes fuse with lysosomes to generate phagolysosomes, which play a key role in enzymatic digestion of the internalized contents into component parts. Recent findings indicate that a simple paradigm of a single cognate receptor interaction that guides the phagosome to phagolysosome formation belies the complexity of combinatorial receptor recognition and diversity of phagosome function. In fact, phagosomes are comprised of hundreds of proteins that play a key role in deciphering the contents of the phagosome and in defining host response. In this review we discuss how the challenge of recognizing diverse molecular patterns is met by combinatorial interactions between phagocytic receptors. Furthermore, these combinations are dynamic and both sculpt the balance between a proinflammatory or anti-inflammatory response and direct phagosome diversity. We also indicate an important role for genetically tractable model organisms in defining key components of this evolutionarily conserved process.
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Affiliation(s)
- Lynda M Stuart
- Laboratory of Developmental Immunology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
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182
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Mallat M, Marín-Teva JL, Chéret C. Phagocytosis in the developing CNS: more than clearing the corpses. Curr Opin Neurobiol 2005; 15:101-7. [PMID: 15721751 DOI: 10.1016/j.conb.2005.01.006] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Cell corpses generated during CNS development are eliminated through phagocytosis performed by a variety of cells, including mesenchyme-derived macrophages and microglia, or glial cells originating in the neurogenic ectoderm. Mounting evidence indicates that in different species, phagocytes not only clear cell corpses but also engulf still-living neural cells or axons, and thereby promote cell death or axon pruning. Knowledge of the mechanisms of corpse recognition by engulfing cells provides molecular signals to this new role for phagocytes. These observations support a conserved and instructive role for phagocytosis in the execution of regressive events during neurogenesis.
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Affiliation(s)
- Michel Mallat
- Biologie des Interactions Neurone-glie, INSERM U.495, IFR 70, UPMC, Hôpital de la Salpêtrière, 47 boulevard de l'Hôpital, 75013 Paris, France.
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183
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Joshi P, Eisenmann DM. The Caenorhabditis elegans pvl-5 gene protects hypodermal cells from ced-3-dependent, ced-4-independent cell death. Genetics 2005; 167:673-85. [PMID: 15238520 PMCID: PMC1470927 DOI: 10.1534/genetics.103.020503] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Programmed cell death (PCD) is regulated by multiple evolutionarily conserved mechanisms to ensure the survival of the cell. Here we describe pvl-5, a gene that likely regulates PCD in Caenorhabditis elegans. In wild-type hermaphrodites at the L2 stage there are 11 Pn.p hypodermal cells in the ventral midline arrayed along the anterior-posterior axis and 6 of these cells become the vulval precursor cells. In pvl-5(ga87) animals there are fewer Pn.p cells (average of 7.0) present at this time. Lineage analysis reveals that the missing Pn.p cells die around the time of the L1 molt in a manner that often resembles the programmed cell deaths that occur normally in C. elegans development. This Pn.p cell death is suppressed by mutations in the caspase gene ced-3 and in the bcl-2 homolog ced-9, suggesting that the Pn.p cells are dying by PCD in pvl-5 mutants. Surprisingly, the Pn.p cell death is not suppressed by loss of ced-4 function. ced-4 (Apaf-1) is required for all previously known apoptotic cell deaths in C. elegans. This suggests that loss of pvl-5 function leads to the activation of a ced-3-dependent, ced-4-independent form of PCD and that pvl-5 may normally function to protect cells from inappropriate activation of the apoptotic pathway.
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Affiliation(s)
- Pradeep Joshi
- Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, 21250, USA
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184
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Vaughan AT, Betti CJ, Villalobos MJ, Premkumar K, Cline E, Jiang Q, Diaz MO. Surviving apoptosis: a possible mechanism of benzene-induced leukemia. Chem Biol Interact 2005; 153-154:179-85. [PMID: 15935815 DOI: 10.1016/j.cbi.2005.03.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The pathological consequences resulting from deregulation of the apoptotic program include cancer (too little apoptosis) or diseases of cell deprivation, such as Alzheimer's (too much apoptosis). We have identified an additional pathology whereby cells reaching the earliest stage of chromatin cleavage have the potential to suppress apoptotic execution and survive. One specific cleavage event associated with this process is restricted to a location within the mixed lineage leukemia (MLL) gene at 11q23. The site of cleavage is consistent with the location where large, approximately 50 kbp loops of supercoiled DNA are attached to the nuclear matrix. Cells modified by this process generate MLL translocations, as shown by inverse PCR, that survive for days to weeks but which have no known relationship with clinical disease. Using a specific approach, cells stimulated by anti-CD95 antibody, a potent stimulator of the apoptotic program, facilitated creation of the MLL-AF9 fusion gene. Further, this rearrangement, which is commonly observed in patients with AML linked to exposure to cytotoxic agents, was efficiently transcribed in cells that were able to undergo cell division. These data are discussed in the context of benzene and benzene metabolite toxicity that impacts the process of apoptosis and is known to lead to leukemic disease.
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Affiliation(s)
- Andrew T Vaughan
- Department of Radiation Oncology, University of California, Davis, 4501 X Street, Suite G 126, Sacramento, CA 95817, USA.
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185
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Jagasia R, Grote P, Westermann B, Conradt B. DRP-1-mediated mitochondrial fragmentation during EGL-1-induced cell death in C. elegans. Nature 2005; 433:754-60. [PMID: 15716954 DOI: 10.1038/nature03316] [Citation(s) in RCA: 260] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2004] [Accepted: 01/06/2005] [Indexed: 02/06/2023]
Abstract
Genetic analyses in Caenorhabditis elegans have been instrumental in the elucidation of the central cell-death machinery, which is conserved from C. elegans to mammals. One possible difference that has emerged is the role of mitochondria. By releasing cytochrome c, mitochondria are involved in the activation of caspases in mammals. However, there has previously been no evidence that mitochondria are involved in caspase activation in C. elegans. Here we show that mitochondria fragment in cells that normally undergo programmed cell death during C. elegans development. Mitochondrial fragmentation is induced by the BH3-only protein EGL-1 and can be blocked by mutations in the bcl-2-like gene ced-9, indicating that members of the Bcl-2 family might function in the regulation of mitochondrial fragmentation in apoptotic cells. Mitochondrial fragmentation is independent of CED-4/Apaf-1 and CED-3/caspase, indicating that it occurs before or simultaneously with their activation. Furthermore, DRP-1/dynamin-related protein, a key component of the mitochondrial fission machinery, is required and sufficient to induce mitochondrial fragmentation and programmed cell death during C. elegans development. These results assign an important role to mitochondria in the cell-death pathway in C. elegans.
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Affiliation(s)
- Ravi Jagasia
- Max Planck Institute of Neurobiology, Am Klopferspitz 18a, D-82152 Planegg-Martinsried, Germany
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186
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Abstract
Programmed cell death, or apoptosis, is a genetically controlled process of cell suicide that is a common fate during an animal's life. In metazoans, apoptotic cells are rapidly removed from the body through the process of phagocytosis. Genetic analyses probing the mechanisms controlling the engulfment of apoptotic cells were pioneered in the nematode Caenorhabditis elegans. So far, at least seven genes have been identified that are required for the recognition and engulfment of apoptotic cells and have been shown to function in two partially redundant signaling pathways. Molecular characterization of their gene products has lead to the finding that similar genes act to control the same processes in other organisms, including mammals. In this paper, we review these exciting findings in C. elegans and discuss their implications in understanding the clearance of apoptotic cells in mammals.
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Affiliation(s)
- Paolo M Mangahas
- Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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187
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Liao DJ. The scavenger cell hypothesis of apoptosis: Apoptosis redefined as a process by which a cell in living tissue is destroyed by phagocytosis. Med Hypotheses 2005; 65:23-8. [PMID: 15893111 DOI: 10.1016/j.mehy.2005.01.028] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2005] [Accepted: 01/27/2005] [Indexed: 01/07/2023]
Abstract
Current literature on the definition and description of apoptosis is very confusing and erratic, due to voluminous studies in recent decades using cell culture technique. Apoptosis has evolved as a programmed mechanism of cell demise to get rid of the cells that are no longer needed by the body. The most important reason for a creature to use this mechanism to kill cells is to avoid inflammatory response that causes tissue damage and ensuing scar formation, as seen in necrosis. To reach this aim, the dying cell communicates, at early stages of the dying process, with macrophages or its neighboring cells that have phagocytotic ability, coined collectively as scavenger cells herein. The dying cell is swiftly engulfed by a scavenger cell without leaking any noxious cellular components into the intercellular space to provoke an inflammatory response. Thus, apoptosis is a process involving at least one other cell type and is actually a mechanism occurring in live tissue. Most studies of apoptosis in recent decades neglect this fundamental point and use cell culture system with a single cell type in the medium, in which avoidance of inflammatory response and tissue damage is no longer a reason. In culture, the dying cell has no way to signal scavenger cells to engulf itself and thus needs to demobilize a series of special mechanisms, which have no need in live tissue, to complete the suicidal process and clearance of its own corpse. These "otherwise-no-need" mechanisms seem to involve activation of executor caspases by cytochrome c, and the activated caspases mediate late processes of apoptosis in vitro. However, because the late processes of apoptosis in vivo actually occur in a phagosome of scavenger cell, it may be phagosomal enzymes, but not executor caspases of the apoptotic cell origin, that are really involved in apoptosis. Therefore, I propose a "scavenger cell hypothesis of apoptosis" to redefine apoptosis as an in vivo mechanism of cell death, and suggest that programmed cell death in culture in a third cell demise mechanism besides necrosis and apoptosis that should be defined using other nomenclatures.
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Affiliation(s)
- D Joshua Liao
- Department of Pathology, Wayne State University School of Medicine and Karmanos Cancer Institute, Detroit, 110 E. Warren Avenue, MI 48201, USA.
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188
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Shoshan Y, Mevorach D. Accelerated autoimmune disease in MRL/MpJ-Fas(lpr) but not in MRL/MpJ following immunization with high load of syngeneic late apoptotic cells. Autoimmunity 2004; 37:103-9. [PMID: 15293880 DOI: 10.1080/08916930410001666622] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Numerous studies have shown that autoantigens may be clustered in the blebs of apoptotic cells. However, it is not yet clear in what circumstances apoptotic cells could be immunogenic rather than tolerogenic when interacting with macrophages, dendritic cells, and B cells. In order to further study this question we compared immunization of high load of syngeneic late apoptotic cells in two genetically close pro-autoimmune mice strains: MRL/MpJ and MRL/MpJ-Fas(lpr). We show that high apoptotic load could accelerate the generation of anti-dsDNA and anticardiolipin, and the extent of kidney disease, in MRL/MpJ-Fas(lpr) but could not generate autoimmunity in MRL/MpJ. Thus, in this model, a high load of apoptotic cells could augment the autoimmune response in established autoimmunity, but did not generate de novo autoimmune response in pro-autoimmune mice. Taken together with previous observations, apoptotic cell load may modify autoimmune disease generating either immune inhibition and down regulation of autoimmunity or immune stimulation and acceleration of an autoimmune disease.
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Affiliation(s)
- Yigal Shoshan
- The Laboratory for Cellular and Molecular Immunology, The Rheumatology Unit, Department of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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189
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Schumacher B, Schertel C, Wittenburg N, Tuck S, Mitani S, Gartner A, Conradt B, Shaham S. C. elegans ced-13 can promote apoptosis and is induced in response to DNA damage. Cell Death Differ 2004; 12:153-61. [PMID: 15605074 DOI: 10.1038/sj.cdd.4401539] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The p53 tumor suppressor promotes apoptosis in response to DNA damage. Here we describe the Caenorhabditis elegans gene ced-13, which encodes a conserved BH3-only protein. We show that ced-13 mRNA accumulates following DNA damage, and that this accumulation is dependent on an intact C. elegans cep-1/p53 gene. We demonstrate that CED-13 protein physically interacts with the antiapoptotic Bcl-2-related protein CED-9. Furthermore, overexpression of ced-13 in somatic cells leads to the death of cells that normally survive, and this death requires the core apoptotic pathway of C. elegans. Recent studies have implicated two BH3-only proteins, Noxa and PUMA, in p53-induced apoptosis in mammals. Our studies suggest that in addition to the BH3-only protein EGL-1, CED-13 might also promote apoptosis in the C. elegans germ line in response to p53 activation. We propose that an evolutionarily conserved pathway exists in which p53 promotes cell death by inducing expression of two BH3-only genes.
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Affiliation(s)
- B Schumacher
- Max-Planck-Institute of Biochemistry, Am Klopferspitz 18A, 82152 Martinsried, Germany
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190
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Chodniewicz D, Klemke RL. Regulation of integrin-mediated cellular responses through assembly of a CAS/Crk scaffold. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2004; 1692:63-76. [PMID: 15246680 DOI: 10.1016/j.bbamcr.2004.03.006] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 11/03/2003] [Accepted: 03/16/2004] [Indexed: 01/09/2023]
Abstract
The molecular coupling of CAS and Crk in response to integrin activation is an evolutionary conserved signaling module that controls cell proliferation, survival and migration. However, when deregulated, CAS/Crk signaling also contributes to cancer progression and developmental defects in humans. Here we highlight recent advances in our understanding of how CAS/Crk complexes assemble in cells to modulate the actin cytoskeleton, and the molecular mechanisms that regulate this process. We discuss in detail the spatiotemporal dynamics of CAS/Crk assembly and how this scaffold recruits specific effector proteins that couple integrin signaling networks to the migration machinery of cells. We also highlight the importance of CAS/Crk signaling in the dual regulation of cell migration and survival mechanisms that operate in invasive cells during development and pathological conditions associated with cancer metastasis.
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Affiliation(s)
- David Chodniewicz
- Department of Immunology, The Scripps Research Institute, 10550 North Torrey Pines Road, SP231, La Jolla, CA 92037, USA
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191
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Bellucci A, Westwood AJ, Ingram E, Casamenti F, Goedert M, Spillantini MG. Induction of inflammatory mediators and microglial activation in mice transgenic for mutant human P301S tau protein. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 165:1643-52. [PMID: 15509534 PMCID: PMC1618683 DOI: 10.1016/s0002-9440(10)63421-9] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/15/2004] [Indexed: 11/22/2022]
Abstract
Mice transgenic for human P301S tau protein exhibit many characteristics of the human tauopathies, including the formation of abundant filaments made of hyperphosphorylated tau protein and neurodegeneration leading to nerve cell loss. At 5 months of age, the pathological changes are most marked in brainstem and spinal cord. Here we show that these changes are accompanied by marked neuroinflammation. Many tau-positive nerve cells in brainstem and spinal cord were strongly immunoreactive for interleukin-1beta and cyclooxygenase-2, indicating induction and overproduction of proinflammatory cytokines and enzymes. In parallel, numerous activated microglial cells were present throughout brain and spinal cord of transgenic mice, where they concentrated around tau-positive nerve cells. These findings suggest that inflammation may play a significant role in the events leading to neurodegeneration in the tauopathies and that anti-inflammatory compounds may have therapeutic potential.
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Affiliation(s)
- Arianna Bellucci
- Brain Repair Centre, University of Cambridge, Robinson Way, Cambridge CB2 2PY, UK
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192
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Abstract
Programmed cell death involves the removal of cell corpses by other cells in a process termed engulfment. Genetic studies of the nematode Caenorhabditis elegans have led to a framework not only for the killing step of programmed cell death but also for the process of cell-corpse engulfment. This work has defined two signal transduction pathways that act redundantly to control engulfment. Signals expressed by dying cells probably regulate these C. elegans pathways. Components of the cell-corpse recognition system of one of the C. elegans pathways include the CED-7 ABC transporter, which likely presents a death ligand on the surface of the dying cell; the CED-1 transmembrane receptor, which recognizes this signal; and the CED-6 adaptor protein, which may transduce a signal from CED-1. The second C. elegans pathway acts in parallel and involves a novel Rac GTPase signaling pathway, with the components CED-2 CrkII, CED-5 DOCK180, CED-12 ELMO, and CED-10 Rac. The cell-corpse recognition system that activates this pathway remains to be characterized. In C. elegans, and possibly in mammals, the process of cell-corpse engulfment promotes the death process itself. The known mechanisms for cell-corpse engulfment leave much to be discovered concerning this fundamental aspect of metazoan biology.
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Affiliation(s)
- Peter W Reddien
- Dept. of Neurobiology and Anatomy,University of Utah School of Medicine, Salt Lake City, Utah 84132, USA.
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193
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Runko E, Kaprielian Z. Caenorhabditis elegans VEM-1, a novel membrane protein, regulates the guidance of ventral nerve cord-associated axons. J Neurosci 2004; 24:9015-26. [PMID: 15483120 PMCID: PMC6730045 DOI: 10.1523/jneurosci.2385-04.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2004] [Revised: 08/26/2004] [Accepted: 08/26/2004] [Indexed: 11/21/2022] Open
Abstract
In the developing CNS, pathfinding growth cones use intermediate target- and pioneer axon-associated guidance cues to navigate along stereotypical trajectories. We previously showed that the novel membrane-associated protein Vema is localized to the floor plate and the optic chiasm, intermediate targets located at the ventral midline of the spinal cord and diencephalon in the developing rodent CNS, respectively. Here, we report that the Caenorhabditis elegans ortholog of vema, vem-1, is expressed by the AVG pioneer midline neuron and by several neurons that extend longitudinally projecting axons into the ventral nerve cord (VNC). In vem-1 mutants and vem-1 (RNAi) animals, a subset of posteriorly projecting interneuron axons either fail to extend ventrally to the VNC and, instead, assume aberrant lateral positions or are inappropriately located in the left tract of the VNC. In addition, ventral motor neuron axons exhibit pathfinding errors within the VNC and along the dorsoventral body axis. The conserved UNC-40/DCC and SAX-3-/Robo receptors mediate signaling events that regulate axon guidance in a wide variety of systems. Double-mutant analyses reveal that vem-1 genetically interacts with unc-40 and is likely to function in parallel with sax-3 to regulate the guidance of a subset of VNC-associated interneuron and motor neuron axons. Consistent with these genetic data, we also show that VEM-1 is capable of physically interacting with UNC-40 but not SAX-3.
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Affiliation(s)
- Erik Runko
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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194
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Gregory CD, Devitt A. The macrophage and the apoptotic cell: an innate immune interaction viewed simplistically? Immunology 2004; 113:1-14. [PMID: 15312130 PMCID: PMC1782541 DOI: 10.1111/j.1365-2567.2004.01959.x] [Citation(s) in RCA: 210] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Macrophages play important roles in the clearance of dying and dead cells. Typically, and perhaps simplistically, they are viewed as the professional phagocytes of apoptotic cells. Clearance by macrophages of cells undergoing apoptosis is a non-phlogistic phenomenon which is often associated with actively anti-inflammatory phagocyte responses. By contrast, macrophage responses to necrotic cells, including secondarily necrotic cells derived from uncleared apoptotic cells, are perceived as proinflammatory. Indeed, persistence of apoptotic cells as a result of defective apoptotic-cell clearance has been found to be associated with the pathogenesis of autoimmune disease. Here we review the mechanisms by which macrophages interact with, and respond to, apoptotic cells. We suggest that macrophages are especially important in clearing cells at sites of histologically visible, high-rate apoptosis and that, otherwise, apoptotic cells are removed largely by non-macrophage neighbours. We challenge the view that necrotic cells, including persistent apoptotic cells are, of necessity, proinflammatory and immunostimulatory and suggest that, under appropriate circumstances, persistent apoptotic cells can provide a prolonged anti-inflammatory stimulus.
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Affiliation(s)
- Christopher D Gregory
- University of Edinburgh MRC Centre for Inflammation Research, College of Medicine and Veterinary Medicine, UK.
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195
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Yeo W, Gautier J. Early neural cell death: dying to become neurons. Dev Biol 2004; 274:233-44. [PMID: 15385155 DOI: 10.1016/j.ydbio.2004.07.026] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Revised: 07/23/2004] [Accepted: 07/28/2004] [Indexed: 10/26/2022]
Abstract
The importance of programmed cell death (PCD) during vertebrate development has been well established. During the development of the nervous system in particular, neurotrophic cell death in innervating neurons matches the number of neurons to the size of their target field. However, PCD also occurs during earlier stages of neural development, within populations of proliferating neural precursors and newly postmitotic neuroblasts, all of which are not yet fully differentiated. This review addresses early neural PCD, which is distinct from neurotrophic death in differentiated neurons. Although early neural PCD is observed in a range of organisms, from Caenorhabditis elegans to mouse, the role and the regulation of early neural PCD are not well understood. The regulation of early neural PCD can be inferred from the function of factors such as bone morphogenetic proteins (BMPs), Wnts, fibroblast growth factors (FGFs), and Sonic Hedgehog (Shh), which regulate both early neural development and PCD occurring in other developmental processes. Cell number control, removal of damaged or misspecified cells (spatially or temporally), and selection are the proposed roles early neural PCDs play during neural development. Data from developmental PCD in C. elegans and Drosophila provide insights into the possible signaling pathways integrating PCD with other processes during early neural development and the roles they might play.
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Affiliation(s)
- Weeteck Yeo
- Department of Genetics and Development, Columbia University, New York, NY 10032, USA
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196
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Voskoboynik A, Rinkevich B, Weiss A, Moiseeva E, Reznick AZ. Macrophage involvement for successful degeneration of apoptotic organs in the colonial urochordate Botryllus schlosseri. ACTA ACUST UNITED AC 2004; 207:2409-16. [PMID: 15184513 DOI: 10.1242/jeb.01045] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Apoptosis is an important tool for shaping developing organs and for maintaining cellular homeostasis. In the colonial urochordate Botryllus schlosseri, apoptosis is also the hallmark end point in blastogenesis, a cyclical and weekly developmental phenomenon. Then the entire old generation of zooids are eliminated (resorbed) by a process that lasts 24-36 h. Administration of the antioxidant butylated hydroxytoluene (BHT) resulted in resorption being arrested by 1-8 days on average. At high doses (2.5-15.0 mg BHT l(-1)) resorption was completed only after removal of BHT. Colonies that were not removed in time, died. In treated colonies, although DNA fragmentation was high, tissues and organs that would normally have died, survived, and the general oxidative levels of lipids were reduced. Blood vessels were widened, containing aggregates of blood cells with a significantly increased proportion of empty macrophage-like cells without inclusion. In colonies rescued from BHT treatment, resorption of zooids started immediately and was completed within a few days. We propose three possible mechanisms as to how BHT may affect macrophage activity: (1) by interrupting signals that further promote apoptosis; (2) through the respiratory burst initiated following a phagocytic stimulus; and (3) by reducing lipid oxidation and changing cell surface markers of target cells. Our results point, for the first time, to the role of phagocytic cells in the coordination of death and clearance signals in blastogenesis.
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Affiliation(s)
- Ayelet Voskoboynik
- Department of Anatomy and Cell Biology, The Bruce Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa
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197
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Michalopoulou S, Micheva I, Kouraklis-Symeonidis A, Kakagianni T, Symeonidis A, Zoumbos NC. Impaired clonogenic growth of myelodysplastic bone marrow progenitors in vitro is irrelevant to their apoptotic state. Leuk Res 2004; 28:805-12. [PMID: 15203278 DOI: 10.1016/j.leukres.2003.12.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2003] [Accepted: 12/14/2003] [Indexed: 11/26/2022]
Abstract
Excessive intramedullary apoptosis has been considered to account for the paradox of hypercellular marrow and refractory cytopenias in myelodysplastic syndrome (MDS). However, a causative relationship of apoptosis to the progenitor's defective clonogenic growth has not been sufficiently demonstrated. We investigated the degree of apoptosis and its contribution to ineffective hematopoiesis in MDS, by assessing the differential clonogenic capacity of purified "apoptotic" and "non-apoptotic" bone marrow progenitors in a short-term semisolid culture system. Although increased apoptosis was indeed detected in MDS bone marrow progenitors, there was no correlation between the existence of apoptosis and culture performance. Non-apoptotic as well as apoptotic CD34+ cells gave similar patterns of growth, both defective compared to normal. The ability of "apoptotic" CD34+ cells to proceed in colony formation as well as the abnormal growth of "non-apoptotic" progenitors are probably pointing towards the need to reconsider the role of apoptosis in the defective clonogenicity of MDS.
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Affiliation(s)
- Sotiria Michalopoulou
- Hematology Division, Department of Internal Medicine, Patras University Medical School, Patras 26500, Greece
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198
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Mishra OP, Delivoria-Papadopoulos M. ATP and cytochrome c-dependent inhibition of caspase-9 activity in the cerebral cortex of newborn piglets. Neurosci Lett 2004; 364:119-23. [PMID: 15196691 DOI: 10.1016/j.neulet.2004.04.026] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2004] [Revised: 04/09/2004] [Accepted: 04/10/2004] [Indexed: 11/18/2022]
Abstract
The present study investigates the mechanism of activation of caspase-9 during hypoxia and tests the hypothesis that ATP and cytochrome c regulate the activity of caspase-9 in the cerebral cortex of newborn piglets. Cerebral tissue hypoxia was documented by decreased levels of high energy phosphates, ATP and phosphocreatine (PCr). Cytosolic fractions were prepared from cerebral cortices and passed through a G50 column, to remove endogenous ATP and cytochrome c. Caspase-9 activity was determined spectrofluorometrically using a specific fluorogenic substrate for caspase-9 at increasing concentrations of ATP (0-1.0 mM) or cytochrome c (0-3.0 microM). Caspase-9 activity (nmol/mg protein/h) was 1.26 +/- 0.15 in the normoxic and 2.13 +/- 0.14 in the hypoxic group (P < 0.05). The enzyme activity was inhibited by ATP or cytochrome c in both normoxic and hypoxic groups. The IC50 for ATP and cytochrome c increased 5-fold and 1.5-fold, respectively, following hypoxia, suggesting a hypoxia-induced modification of the ATP and cytochrome binding sites. The data demonstrate that ATP (1 mM) and cytochrome c (3.0 microM) inhibit caspase-9 activity by approximately 70%. On the basis of these observations, we propose a new and novel concept that the caspase-9 activity remains inhibited under the normoxic conditions and during hypoxia the decrease in ATP and decreases in the affinity for ATP and cytochrome c release the inhibitory block to activate the enzyme. Results of ATP- and cytochrome c-dependent inhibition of purified caspase-9 human recombinant show that the inhibitory effect by ATP and cytochrome c does not require Apaf-1. To our knowledge, this is a completely new concept and a new mechanism of regulation of caspase-9 activity that may lead to hypoxia-induced programmed cell death.
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Affiliation(s)
- Om P Mishra
- Department of Pediatrics, Drexel University College of Medicine and St. Christopher's Hospital for Children, Philadelphia, PA 19129, USA.
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199
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Abstract
The efficient elimination of apoptotic cells is crucial for tissue homeostasis in multicellular organisms. Secreted "find-me," exposed "eat-me," and lacking "don't-eat-me" signals comprise the central elements of apoptotic cell removal, thus preventing the release of intracellular contents into the surrounding tissue. This is of special importance, as there is growing evidence that the onset of autoimmune disorders can be linked to the inefficient removal of apoptotic cells. This review focuses on the signals displayed by apoptotic cells, the bridging and receptor molecules on the phagocyte, and is intended to present a simplified model of the phagocytic synapse. Additionally, the recent discovery of lysophosphatidylcholine functioning as soluble attraction signal is discussed in the general context of apoptotic cell clearance.
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Affiliation(s)
- Kirsten Lauber
- Department of Internal Medicine I, University of Tuebingen, D-72076 Tuebingen, Germany
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200
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Watts RJ, Schuldiner O, Perrino J, Larsen C, Luo L. Glia engulf degenerating axons during developmental axon pruning. Curr Biol 2004; 14:678-84. [PMID: 15084282 DOI: 10.1016/j.cub.2004.03.035] [Citation(s) in RCA: 174] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Revised: 02/10/2004] [Accepted: 02/10/2004] [Indexed: 01/30/2023]
Abstract
Developmental axon pruning is widely used in constructing the nervous system. Accordingly, diverse mechanisms are likely employed for various forms of axon pruning. In the Drosophila mushroom bodies (MB), gamma neurons initially extend axon branches into both the dorsal and medial MB axon lobes in larvae. Through a well-orchestrated set of developmental events during metamorphosis, axon branches to both lobes degenerate prior to the formation of adult connections. Here, we analyze ultrastructural changes underlying axon pruning by using a genetically encoded electron microscopic (EM) marker to selectively label gamma neurons. By inhibiting axon pruning in combination with the use of this EM marker, we demonstrate a causal link between observed cellular events and axon pruning. These events include changes in axon ultrastructure, synaptic degeneration, and engulfment of degenerating axon fragments by glia for their subsequent breakdown via the endosomal-lysosomal pathway. Interestingly, glia selectively invade MB axon lobes at the onset of metamorphosis; this increase in cell number is independent of axon fragmentation. Our study reveals a key role for glia in the removal of axon fragments during developmental axon pruning.
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Affiliation(s)
- Ryan J Watts
- Department of Biological Sciences, Stanford University, Stanford, CA 94305 USA
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