scholarly journals Polyomavirus Small T Antigen Induces Apoptosis in Mammalian Cells through the UNC5B Pathway in a PP2A-Dependent Manner

2020 ◽  
Vol 94 (14) ◽  
Author(s):  
Sameer Ahmed Bhat ◽  
Zarka Sarwar ◽  
Syed Qaaifah Gillani ◽  
Misbah Un Nisa ◽  
Irfana Reshi ◽  
...  
Keyword(s):  
Cell Death ◽  
Mammalian Cells ◽  
Mitotic Arrest ◽  
T Antigen ◽  
Mitotic Catastrophe ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Antibody Treatment ◽  
Small T Antigen ◽  
Apoptotic Activity

ABSTRACT UNC5B is a dependence receptor that promotes survival in the presence of its ligand, netrin-1, while inducing cell death in its absence. The receptor has an important role in the development of the nervous and vascular systems. It is also involved in the normal turnover of intestinal epithelium. Netrin-1 and UNC5B are deregulated in multiple cancers, including colorectal, neuroblastoma, and breast tumors. However, the detailed mechanism of UNC5B function is not fully understood. We have utilized the murine polyomavirus small T antigen (PyST) as a tool to study UNC5B-mediated apoptosis. PyST is known to induce mitotic arrest followed by extensive cell death in mammalian cells. Our results show that the expression of PyST increases mRNA levels of UNC5B by approximately 3-fold in osteosarcoma cells (U2OS) and also stabilizes UNC5B at the posttranslational level. Furthermore, UNC5B is upregulated predominantly in those cells that undergo mitotic arrest upon PyST expression. Interestingly, although its expression was previously reported to be regulated by p53, our data show that the increase in UNC5B levels by PyST is p53 independent. The posttranslational stabilization of UNC5B by PyST is regulated by the interaction of PyST with PP2A. We also show that netrin-1 expression, which is known to inhibit UNC5B apoptotic activity, promotes survival of PyST-expressing cells. Our results thus suggest an important role of UNC5B in small-T antigen-induced mitotic catastrophe that also requires PP2A. IMPORTANCE UNC5B, PP2A, and netrin-1 are deregulated in a variety of cancers. UNC5B and PP2A are regarded as tumor suppressors, as they promote apoptosis and are deleted or mutated in many cancers. In contrast, netrin-1 promotes survival by inhibiting dependence receptors, including UNC5B, and is upregulated in many cancers. Here, we show that UNC5B-mediated apoptosis can occur independently of p53 but in a PP2A-dependent manner. A substantial percentage of cancers arise due to p53 mutations and are insensitive to chemotherapeutic treatments that activate p53. Unexpectedly, treatment of cancers having functional p53 with many conventional drugs leads to the upregulation of netrin-1 through activated p53, which is counterintuitive. Therefore, understanding the p53-independent mechanisms of the netrin-UNC5B axis, such as those involving PP2A, assumes greater clinical significance. Anticancer strategies utilizing anti-netrin-1 antibody treatment are already in clinical trials.

scholarly journals Polyoma small T antigen triggers cell death via mitotic catastrophe

Oncogene ◽  
2014 ◽  
Vol 34 (19) ◽  
pp. 2483-2492 ◽  
Author(s):  
A T Pores Fernando ◽  
S Andrabi ◽  
O Cizmecioglu ◽  
C Zhu ◽  
D M Livingston ◽  
...  
Keyword(s):  
Cell Death ◽  
T Antigen ◽  
Mitotic Catastrophe ◽  
Small T Antigen

scholarly journals Debcl, a Proapoptotic Bcl-2 Homologue, Is a Component of the Drosophila melanogaster Cell Death Machinery

2000 ◽  
Vol 148 (4) ◽  
pp. 703-714 ◽  
Author(s):  
Paul A. Colussi ◽  
Leonie M. Quinn ◽  
David C.S. Huang ◽  
Michelle Coombe ◽  
Stuart H. Read ◽  
...  
Keyword(s):  
Cell Death ◽  
Drosophila Melanogaster ◽  
Mammalian Cells ◽  
Cultured Cells ◽  
Gene Dosage ◽  
Family Members ◽  
Ectopic Expression ◽  
Dependent Manner ◽  
Proapoptotic Protein ◽  
Main Components

Bcl-2 family of proteins are key regulators of apoptosis. Both proapoptotic and antiapoptotic members of this family are found in mammalian cells, but no such proteins have been described in insects. Here, we report the identification and characterization of Debcl, the first Bcl-2 homologue in Drosophila melanogaster. Structurally, Debcl is similar to Bax-like proapoptotic Bcl-2 family members. Ectopic expression of Debcl in cultured cells and in transgenic flies causes apoptosis, which is inhibited by coexpression of the baculovirus caspase inhibitor P35, indicating that Debcl is a proapoptotic protein that functions in a caspase-dependent manner. debcl expression correlates with developmental cell death in specific Drosophila tissues. We also show that debcl genetically interacts with diap1 and dark, and that debcl-mediated apoptosis is not affected by gene dosage of rpr, hid, and grim. Biochemically, Debcl can interact with several mammalian and viral prosurvival Bcl-2 family members, but not with the proapoptotic members, suggesting that it may regulate apoptosis by antagonizing prosurvival Bcl-2 proteins. RNA interference studies indicate that Debcl is required for developmental apoptosis in Drosophila embryos. These results suggest that the main components of the mammalian apoptosis machinery are conserved in insects.

scholarly journals Liganded Thyroid Hormone Receptor Induces Nucleosome Removal and Histone Modifications to Activate Transcription during Larval Intestinal Cell Death and Adult Stem Cell Development

Endocrinology ◽  
2012 ◽  
Vol 153 (2) ◽  
pp. 961-972 ◽  
Author(s):  
Kazuo Matsuura ◽  
Kenta Fujimoto ◽  
Liezhen Fu ◽  
Yun-Bo Shi
Keyword(s):  
Cell Death ◽  
Gene Regulation ◽  
Thyroid Hormone ◽  
Chromatin Remodeling ◽  
Histone Modifications ◽  
Intestinal Cell ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Vertebrate Development

Thyroid hormone (T3) plays an important role in regulating multiple cellular and metabolic processes, including cell proliferation, cell death, and energy metabolism, in vertebrates. Dysregulation of T3 signaling results in developmental abnormalities, metabolic defects, and even cancer. We used T3-dependent Xenopus metamorphosis as a model to study how T3 regulates transcription during vertebrate development. T3 exerts its metamorphic effects through T3 receptors (TR). TR recruits, in a T3-dependent manner, cofactor complexes that can carry out chromatin remodeling/histone modifications. Whether and how histone modifications change upon gene regulation by TR during vertebrate development is largely unknown. Here we analyzed histone modifications at T3 target genes during intestinal metamorphosis, a process that involves essentially total apoptotic degeneration of the simple larval epithelium and de novo development of the adult epithelial stem cells, followed by their proliferation and differentiation into the complex adult epithelium. We demonstrated for the first time in vivo during vertebrate development that TR induces the removal of core histones at the promoter region and the recruitment of RNA polymerase. Furthermore, a number of histone activation and repression marks have been defined based on correlations with mRNA levels in cell cultures. Most but not all correlate with gene expression induced by liganded TR during development, suggesting that tissue and developmental context influences the roles of histone modifications in gene regulation. Our findings provide important mechanistic insights on how chromatin remodeling affects developmental gene regulation in vivo.

scholarly journals Cell Cycle Progression in Monkey Cells Expressing Simian Virus 40 Small t Antigen from Adenovirus Vectors

1998 ◽  
Vol 72 (12) ◽  
pp. 9637-9644 ◽  
Author(s):  
Alan K. Howe ◽  
Stéphanie Gaillard ◽  
John S. Bennett ◽  
Kathleen Rundell
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Mapk Pathway ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Dependent Manner ◽  
Cycle Progression ◽  
Adenovirus Vectors ◽  
Small T Antigen

ABSTRACT The simian virus 40 small t antigen (small-t) is required for optimal viral replication and transformation, especially during the infection of nondividing cells, suggesting that the function of small-t is to promote cell cycle progression. The mechanism through which small-t promotes cell growth reflects, in part, its binding and inhibition of protein phosphatase 2A (PP2A). The use of recombinant adenoviruses allows small-t expression in a majority of cells in a population, thus providing a convenient source of cells for biochemical analyses. In monkey kidney CV1 cells, small-t expressed from these adenovirus vectors activated the mitogen-activated protein kinase (MAPK) pathway, induced JNK activity, and increased AP-1 DNA-binding activity, all in a PP2A-dependent manner. Expression of small-t also caused an increase in the phosphorylation of the Na+/H+ antiporter, a mitogen-activated ion exchanger whose activity correlates with its phosphorylation. At least part of the antiporter phosphorylation induced by small-t reflected activation of the MAPK pathway, as suggested by results of assays using a chemical inhibitor of the MAPK-activating kinase, MEK. Finally, small-t expression from adenovirus vectors promoted efficient cell cycle progression by growth-arrested cells. These vectors should facilitate further analysis of effects of small-t on cell cycle mediators.

scholarly journals Adiponectin inhibits the production of TNF-alpha, IL-6 and chemokines by human lung macrophages

2021 ◽  
Author(s):  
Helene Salvator ◽  
Stanislas Grassin-Delyle ◽  
Marion Brollo ◽  
Louis-jean Couderc ◽  
Charlotte Abrial ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Mammalian Cells ◽  
Human Lung ◽  
Poly I:C ◽  
Low Molecular Weight ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Adiponectin Receptors ◽  
Lung Macrophages ◽  
The Impact

Background and purpose: Obesity is associated with an elevated risk of severe respiratory infections and inflammatory lung diseases. The objectives were to investigate (i) the production of adiponectin by human lung explants, (ii) the expression of the adiponectin receptors AdipoR1 and AdipoR2 by human lung macrophages (LMs), and (iii) the impact of recombinant human adiponectin and a small-molecule APN receptor agonist (AdipoRon) on LMs activation. Experimental approach: Human parenchyma explants and LMs were isolated from patients operated for carcinoma. The LMs were cultured with recombinant adiponectin or AdipoRon and stimulated with LPS (10 ng.mL-1), poly(I:C) (10 µg.mL-1) or interleukin(IL)-4 (10 ng.mL-1) for 24 h. Cytokines or adiponectin, released by explants or LMs, were measured using ELISAs. The mRNA levels of AdipoR1 and AdipoR2 were determined using real-time quantitative PCR. AdipoRs expression was also assessed with confocal microscopy. Key results: Adiponectin was released by lung explants at a level negatively correlated with the donor’s body mass index. AdipoR1 and AdipoR2 were both expressed in LMs. Adiponectin (3-30 µg.mL-1) and AdipoRon (25-50 μM) markedly inhibited the LPS- and poly(I:C)-induced release of Tumor Necrosis Factor-alpha, IL-6 and chemokines (CCL3, CCL4, CCL5, CXCL1, CXCL8, CXCL10) and the IL-4-induced release of chemokines (CCL13, CCL17, CCL22) in a concentration-dependent manner. Recombinant adiponectin produced in mammalian cells (lacking low molecular weight isoforms) had no effects on LMs. Conclusions and implications: The low-molecular-weight isoforms of adiponectin and AdipoRon have an anti-inflammatory activity in the lung environment. Targeting adiponectin receptors may constitute a new means of controlling airways inflammation.

Interferon-gamma regulation of Clara cell gene expression: in vivo and in vitro

1997 ◽  
Vol 272 (6) ◽  
pp. L1142-L1151 ◽  
Author(s):  
S. M. Magdaleno ◽  
G. Wang ◽  
K. J. Jackson ◽  
M. K. Ray ◽  
S. Welty ◽  
...  
Keyword(s):  
Interferon Gamma ◽  
Potential Interaction ◽  
T Antigen ◽  
Clara Cell ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Sv40 Large T Antigen ◽  
Ifn Gamma

This report demonstrates that Clara cell 10-kDa protein (CC10) mRNA levels are regulated by interferon-gamma (IFN-gamma). An analysis of total lung RNA from mice given IFN-gamma intratracheally showed increased levels of CC10 mRNA compared to control animals but no significant increases in surfactant proteins B and C. These results were confirmed in a Clara cell line, mtCC1-2, generated from the lungs of a transgenic mouse expressing the SV40 large T antigen under the control of a Clara cell-specific promoter. Significant increases in mtCC1-2 CC10 mRNA levels were observed in a time- and a dose-dependent manner. The expression of transacting factors hepatocyte nuclear factors 3 alpha and 3 beta (HNF-3 alpha and HNF-3 beta) were also analyzed, and a transient increase in the expression of HNF-3 beta but not HNF-3 alpha was detected. Deoxyribonuclease I footprint analysis identified a signal transducer and activator of transcription (STAT) binding site (at nucleotides -293 to -284 of CC10) adjacent to two thyroid transcription factor-1 (TTF-1) binding sites, suggesting a potential interaction between STAT1 and TTF-1. This report reinforces the hypothesis that CC10 functions as an anti-inflammatory protein and that increases in CC10 protein may provide additional protection from inflammation and disease in the lung.

scholarly journals Discovery of Sulforaphane as an Inducer of Ferroptosis in U-937 Leukemia Cells: Expanding Its Anticancer Potential

Cancers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 76
Author(s):  
Giulia Greco ◽  
Michael Schnekenburger ◽  
Elena Catanzaro ◽  
Eleonora Turrini ◽  
Fabio Ferrini ◽  
...  
Keyword(s):  
Cell Death ◽  
Apoptotic Cell ◽  
Leukemia Cell ◽  
Kinase Domain ◽  
Apoptotic Cell Death ◽  
Dependent Manner ◽  
Interacting Protein ◽  
Leukemia Cell Lines ◽  
Cell Death Mechanisms ◽  
Apoptotic Activity

In recent years, natural compounds have emerged as inducers of non-canonical cell death. The isothiocyanate sulforaphane (SFN) is a well-known natural anticancer compound with remarkable pro-apoptotic activity. Its ability to promote non-apoptotic cell-death mechanisms remains poorly investigated. This work aimed to explore the capacity of SFN to induce non-apoptotic cell death modalities. SFN was tested on different acute myeloid leukemia cell lines. The mechanism of cell death was investigated using a multi-parametric approach including fluorescence microscopy, western blotting, and flow cytometry. SFN triggered different cell-death modalities in a dose-dependent manner. At 25 μM, SFN induced caspase-dependent apoptosis and at 50 μM ferroptosis was induced through depletion of glutathione (GSH), decreased GSH peroxidase 4 protein expression, and lipid peroxidation. In contrast, necroptosis was not involved in SFN-induced cell death, as demonstrated by the non-significant increase in phosphorylation of receptor-interacting protein kinase 3 and phosphorylation of the necroptotic effector mixed lineage kinase domain-like pseudokinase. Taken together, our results suggest that the antileukemic activity of SFN can be mediated via both ferroptotic and apoptotic cell death modalities.

scholarly journals Induction of Endothelin-2 Expression by Luteinizing Hormone and Hypoxia: Possible Role in Bovine Corpus Luteum Formation

Endocrinology ◽  
2010 ◽  
Vol 151 (4) ◽  
pp. 1914-1922 ◽  
Author(s):  
Eyal Klipper ◽  
Anat Levit ◽  
Yonit Mastich ◽  
Bajram Berisha ◽  
Dieter Schams ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Corpus Luteum ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Low Oxygen ◽  
Vegf Mrna

The pattern and regulation of endothlin-2 (EDN2) expression and its putative roles in bovine ovaries were investigated. EDN2 mRNA was determined in corpus luteum (CL) and during folliculoluteal transition induced by GnRH in vivo. EDN2 was elevated only in the early CL and was not present in older CL. In the young CL, EDN2 mRNA was identified mainly in luteal cells but not endothelial cells that expressed the EDN1 gene. Similarly, in preovulatory follicles, EDN2 was expressed in the granulosa cells (GCs) and not in the vascular theca interna. LH and hypoxia are two major stimulants of CL formation. Therefore, GCs were cultured with bovine LH, under hypoxic conditions. GCs incubated with bovine LH resulted in increased EDN2 mRNA 42 h later. CoCl2, a hypoxia-mimicking agent, elevated EDN2 in GCs in a dose-dependent manner. Incubation of the human GC line (Simian virus 40 large T antigen) under low oxygen tension (1%) augmented EDN2 6 and 24 h later. In these two cell types, along with EDN2, hypoxia augmented VEGF. EDN2 induced in GCs changes that characterize the developing CL: cell proliferation as well as up-regulation of vascular endothelial growth factor and cyclooxygenase-2 (mRNA and protein levels). Human chorionic gonadotropin also up-regulated these two genes. Small interfering RNA targeting EDN-converting enzyme-1 effectively reduced its mRNA levels. This treatment, expected to lower the mature EDN2 peptide production, inhibited VEGF mRNA levels and GC numbers. Together these data suggest that elevated EDN2 in the early bovine CL, triggered by LH surge and hypoxia, may facilitate CL formation by promoting angiogenesis, cell proliferation, and differentiation.

scholarly journals Calpain is required for macroautophagy in mammalian cells

2006 ◽  
Vol 175 (4) ◽  
pp. 595-605 ◽  
Author(s):  
Francesca Demarchi ◽  
Cosetta Bertoli ◽  
Tamara Copetti ◽  
Isei Tanida ◽  
Claudio Brancolini ◽  
...  
Keyword(s):  
Cell Death ◽  
Protein Degradation ◽  
Mammalian Cells ◽  
Apoptotic Cell ◽  
Nuclear Factor Κb ◽  
Early Endosome ◽  
Regulatory Subunit ◽  
Dependent Manner ◽  
Nuclear Factor ◽  
Salvage Pathway

Ubiquitously expressed micro- and millicalpain, which both require the calpain small 1 (CAPNS1) regulatory subunit for function, play important roles in numerous biological and pathological phenomena. We have previously shown that the product of GAS2, a gene specifically induced at growth arrest, is an inhibitor of millicalpain and that its overexpression sensitizes cells to apoptosis in a p53-dependent manner (Benetti, R., G. Del Sal, M. Monte, G. Paroni, C. Brancolini, and C. Schneider. 2001. EMBO J. 20:2702–2714). More recently, we have shown that calpain is also involved in nuclear factor κB activation and its relative prosurvival function in response to ceramide, in which calpain deficiency strengthens the proapoptotic effect of ceramide (Demarchi, F., C. Bertoli, P.A. Greer, and C. Schneider. 2005. Cell Death Differ. 12:512–522). Here, we further explore the involvement of calpain in the apoptotic switch and find that in calpain-deficient cells, autophagy is impaired with a resulting dramatic increase in apoptotic cell death. Immunostaining of the endogenous autophagosome marker LC3 and electron microscopy experiments demonstrate that autophagy is impaired in CAPNS1-deficient cells. Accordingly, the enhancement of lysosomal activity and long-lived protein degradation, which normally occur upon starvation, is also reduced. In CAPNS1-depleted cells, ectopic LC3 accumulates in early endosome-like vesicles that may represent a salvage pathway for protein degradation when autophagy is defective.

scholarly journals The amino-terminal transforming region of simian virus 40 large T and small t antigens functions as a J domain.

1997 ◽  
Vol 17 (8) ◽  
pp. 4761-4773 ◽  
Author(s):  
A Srinivasan ◽  
A J McClellan ◽  
J Vartikar ◽  
I Marks ◽  
P Cantalupo ◽  
...  
Keyword(s):  
Amino Acid ◽  
Atpase Activity ◽  
Mammalian Cells ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Large T Antigen ◽  
Amino Terminal ◽  
J Domain ◽  
Small T Antigen

Simian virus 40 (SV40) encodes two proteins, large T antigen and small t antigen that contribute to virus-induced tumorigenesis. Both proteins act by targeting key cellular regulatory proteins and altering their function. Known targets of the 708-amino-acid large T antigen include the three members of the retinoblastoma protein family (pRb, p107, and p130), members of the CBP family of transcriptional adapter proteins (cap-binding protein [CBP], p300, and p400), and the tumor suppressor p53. Small t antigen alters the activity of phosphatase pp2A and transactivates the cyclin A promoter. The first 82 amino acids of large T antigen and small t antigen are identical, and genetic experiments suggest that an additional target(s) important for transformation interacts with these sequences. This region contains a motif similar to the J domain, a conserved sequence found in the DnaJ family of molecular chaperones. We show here that mutations within the J domain abrogate the ability of large T antigen to transform mammalian cells. To examine whether a purified 136-amino-acid fragment from the T antigen amino terminus acts as a DnaJ-like chaperone, we investigated whether this fragment stimulates the ATPase activity of two hsc70s and discovered that ATP hydrolysis is stimulated four- to ninefold. In addition, ATPase-defective mutants of full-length T antigen, as well as wild-type small t antigen, stimulated the ATPase activity of hsc70. T antigen derivatives were also able to release an unfolded polypeptide substrate from an hsc70, an activity common to DnaJ chaperones. Because the J domain of T antigen plays essential roles in viral DNA replication, transcriptional control, virion assembly, and tumorigenesis, we conclude that this region may chaperone the rearrangement of multiprotein complexes.

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