Why does HAMLET preferentially kill tumor cells? p38-dependent death in tumor but up-regulation of innate immunity in healthy, differentiated cells
ABSTRACT: HAMLET triggers a p38- and ER stress-dependent death response in carcinoma cells. Transcriptome and proteome analysis detected an increase in p38 expression and phosphorylation exclusively in carcinoma cells and p38 inhibitors delayed the death response to HAMLET in carcinoma and lymphoma cells. ER stress gene expression was also increased in tumor cells and HAMLET triggered rapid XBP1 mRNA splicing, eIF2a phosphorylation, and ATF6 cleavage as well as Hsc70 and CHOP activation, suggesting that ER stress caused by HAMLET may trigger p38 phosphorylation and death. The p38 inhibitor reduced the transcription of both p38 and ER stress gene transcription. Healthy differentiated cells, in contrast, showed no alteration in p38 signaling but a rapid innate immune response was detected and the cells survived HAMLET challenge. Overall design: 2 cell lines, time course, HAMLET treatment
Project description:HAMLET triggers a p38- and ER stress-dependent death response in carcinoma cells. Transcriptome and proteome analysis detected an increase in p38 expression and phosphorylation exclusively in carcinoma cells and p38 inhibitors delayed the death response to HAMLET in carcinoma and lymphoma cells. ER stress gene expression was also increased in tumor cells and HAMLET triggered rapid XBP1 mRNA splicing, eIF2a phosphorylation, and ATF6 cleavage as well as Hsc70 and CHOP activation, suggesting that ER stress caused by HAMLET may trigger p38 phosphorylation and death. The p38 inhibitor reduced the transcription of both p38 and ER stress gene transcription. Healthy differentiated cells, in contrast, showed no alteration in p38 signaling but a rapid innate immune response was detected and the cells survived HAMLET challenge. 2 cell lines, time course, HAMLET treatment
Project description:Farnesol (FOH) and other isoprenoid alcohols induce apoptosis in various carcinoma cells and inhibit tumorigenesis in several in vivo models. However, the mechanisms by which these isoprenoids mediate their effects are not yet fully understood. In this study, we show that FOH is effective inducer of apoptosis in several lung carcinoma cells, including H460 cells. This induction is associated with activation of caspase-3, -9, and -12, and cleavage of PARP. To obtain insight into the mechanism involved in FOH-induced apoptosis, we compared the gene expression profiles of FOH-treated and control H460 cells using microarray analysis. This analysis revealed that many of the genes implicated in endoplasmic reticulum (ER) stress, including ATF3, CHOP/GADD153, HERPUD1, BIP (GRP78), XBP1, PDIA4, and TDAG51, were highly up-regulated within 4 hr of FOH treatment suggesting that FOH-induced apoptosis involves an ER-stress response. This was supported by observations showing that treatment with FOH induces phosphorylation of eIF2. FOH induces activation of several MAPK pathways, including p38, MEK-ERK, and JNK. Inhibition of MEK1/2 by U0126 inhibited the induction of ER stress-response genes. In addition, knockdown of the MEK1/2 and JNK1/2 expression by short interfering RNA (siRNA) effectively inhibited the induction of apoptosis and activation of caspase-3 and cleavage of PARP by FOH. However, only MEK1/2 siRNAs reduced the expression of ER stress-related genes and inhibited phosphorylation of eIF2. Our results demonstrate that FOH-induced apoptosis is coupled to ER stress and that activation of MEK1/2 is an upstream event in the FOH-induced ER stress signaling cascade. Vehicle vs. 4h FOH Signature Gene lists (Replicates 1 & 2) are linked as supplementary files to the Series record. Experiment Overall Design: H460 cells were treated for 4 hours with 250 micromolar FOH or vehicle (DMSO) in duplicate experiments. Each FOH treated sample was compared to its matched Vehicle and dye-flips were performed, resulting in 4 arrays (2 replicate sets x 2 technical replicates).
Project description:This model is from the article:
Modelling the Role of the Hsp70/Hsp90 System in the Maintenance of Protein Homeostasis
Proctor CJ, Lorimer IAJ
PLoS ONE2011; 6(7): e22038.
Neurodegeneration is an age-related disorder which is characterised by the accumulation of aggregated protein and neuronal cell death. There are many different neurodegenerative diseases which are classified according to the specific proteins involved and the regions of the brain which are affected. Despite individual differences, there are common mechanisms at the sub-cellular level leading to loss of protein homeostasis. The two central systems in protein homeostasis are the chaperone system, which promotes correct protein folding, and the cellular proteolytic system, which degrades misfolded or damaged proteins. Since these systems and their interactions are very complex, we use mathematical modelling to aid understanding of the processes involved. The model developed in this study focuses on the role of Hsp70 (IPR00103) and Hsp90 (IPR001404) chaperones in preventing both protein aggregation and cell death. Simulations were performed under three different conditions: no stress; transient stress due to an increase in reactive oxygen species; and high stress due to sustained increases in reactive oxygen species. The model predicts that protein homeostasis can be maintained during short periods of stress. However, under long periods of stress, the chaperone system becomes overwhelmed and the probability of cell death pathways being activated increases. Simulations were also run in which cell death mediated by the JNK (P45983) and p38 (Q16539) pathways was inhibited. The model predicts that inhibiting either or both of these pathways may delay cell death but does not stop the aggregation process and that eventually cells die due to aggregated protein inhibiting proteasomal function. This problem can be overcome if the sequestration of aggregated protein into inclusion bodies is enhanced. This model predicts responses to reactive oxygen species-mediated stress that are consistent with currently available experimental data. The model can be used to assess specific interventions to reduce cell death due to impaired protein homeostasis.
Simulations were performed under three different conditions: 1) normal condition (no stress), 2) moderate stress due to an increase in reactive oxygen species (ROS) i.e. ROS levels were increased by a factor of 4 at time=4hours for a period of 1 hour (not 2 hours as mentioned in the figure 5 legend of the reference publication. This is a typo in the paper and is clarified by the author) and 3) high stress due to sustained increase in reactive oxygen species (ROS) (here ROS increases with time).
The model that corresponds to the normal condition is submitted as a main model in the BioModels Database. The other two models, that corresponds to the moderate stress conditions and high stress conditions are available in SBML format as supporting files [go to Curation tab].
Supplementary figures S3 (normal condition), S4 (moderate stress condition) and S6 (high stress condition) are reproduced here.
Project description:Ethylene gas is essential for many developmental processes and stress responses in plants. ETHYLENE INSENSITIVE2 (EIN2), an NRAMP-homologous integral membrane protein, plays an essential role in ethylene signaling but its function remains enigmatic. Here we report that phosphorylation-regulated proteolytic processing of EIN2 triggers its endoplasmic reticulum (ER)-nucleus translocation, which is essential for hormone signaling and response in Arabidopsis. Without ethylene, or in hormone receptors mutants, ER-tethered EIN2 shows CTR1 kinase-dependent phosphorylation. Ethylene exposure triggers dephosphorylation and proteolytic cleavage, resulting in rapid nuclear translocation of a carboxyl-terminal EIN2 fragment (C’). Plants containing mutations that mimic EIN2 dephosphorylation, or inactivate CTR1, show constitutive cleavage and nuclear localization of EIN2-C’, and EIN3/EIL1-dependent activation of ethylene responses. These findings uncover a mechanism of subcellular communication whereby ethylene gas stimulates rapid phosphorylation-dependent cleavage and nuclear movement of the EIN2-C’ peptide, thus linking hormone perception and signaling components located in the ER with nuclear-localized transcriptional regulators.
Project description:Ultraviolet (UV) light radiation induces the formation of bulky photoproducts in the DNA that globally affect transcription and splicing. However, the signaling pathways and mechanisms that link UV light-induced DNA damage to changes in RNA metabolism remain poorly understood. Here, we employ quantitative phosphoproteomics and protein kinase inhibition to provide a systems view on protein phosphorylation patterns induced by UV light, and uncover the dependencies of phosphorylation events on the canonical DNA damage signaling by ATM/ATR and the p38 MAP kinase pathway. We identify RNA binding proteins as primary substrates and 14-3-3 as direct readers of p38-MK2-dependent phosphorylation induced by UV light. Mechanistically, we show that MK2 phosphorylates the RNA binding subunit of the NELF complex NELFE on Serine 115. NELFE phosphorylation promotes the recruitment of 14-3-3 and rapid dissociation of the NELF complex from chromatin, which is accompanied by RNA polymerase II elongation. Overall design: Analysis of RNA pol II occupancy genome-wide in mock-treated U2OS cells and cells exposed to UV light (40 J/m2, 1 hour recovery).
Project description:In response to environmental stressors and a variety of inflammatory cytokines, p38 MAPKs become directly activated. Here we report the human glucocorticoid receptor (GR) Serine 134 as a novel target for p38 MAPK. Unlike most other phosphorylation events that occur on the GR, phosphorylation of Ser134 was found to be hormone-independent in several human and rat cell types. Instead we found phosphorylation of Ser134 was induced by a variety of stress-activating stimuli, including: glucose starvation, ultraviolet irradiation, osmotic shock, and oxidative stress. Pharmacological inhibitors and shRNA-mediated knockdown experiments correlate this phosphorylation with the activation of p38 MAPK. Compared to wild-type GR, cells expressing a mutant receptor incapable of phosphorylation at Ser134 (S134A GR) had a significantly altered hormone-dependent genome-wide transcriptional response to glucocorticoids. Moreover, we show that although WT GR regulated roughly half as many genes as S134A GR, WT receptor selectively activated significantly more genes associated with endocrine and inflammatory disease than the mutant receptor, suggesting that the phosphorylation status of Ser134 is critical for modulating GR function. Phosphorylation of Ser134 did not alter either nuclear translocation or the stability of the GR protein in the absence or presence of ligand. However, phosphorylation of Ser134 significantly increased the association of the GR with the zeta isoform the 14-3-3 class of signaling proteins, resulting in a blunted hormone-dependent transcriptional response of LAD1 and IGFBP1 but not GILZ. Together these data suggest that the phosphorylation of Ser134 acts as a molecular sensor on the GR, monitoring the level of cellular stress to allow for altered 14-3-3zeta cofactor association, ultimately modifying glucocorticoid signaling in a gene-dependent manner. Our results reveal one mechanism that may allow cellular stress to dictate the transcriptional response of cells to hormone. U2OS cells, a human osteosarcoma cell line, were transfected with either WT GR or S134A GR and put under antibiotic selection to produce a stable mixed population of cells expressing comparable levels of GR. 10^6 cells were treated with 100nM Dexamethasone (DEX) or vehicle control for 6 hours. Three biological and one hybridization replicate are included for each sample.
Project description:In order to elucidate how FOXOs affect diverse cellular processes such as cell cycle progression, stress response and transformation we made use of an inducible version of the FOXO3a protein fused to the hormone binding domain of the human estrogen receptor (FOXO3a-A3-ER) in which all three Akt phosphorylation sites have been mutated to alanine. FOXO3a.A3-ER was stably expressed in the human colon carcinoma cell line DLD-1 (Kops et al., 2002b). In order to analyse the transcriptional response to FOXO3a activation we generated gene expression profiles from DL23 or parental DLD-1 cells, after 6 or 24 hours of 4-OHT treatment using cDNA microarrays.
Project description:Targeting protein kinase C (PKC) isoforms by the small molecule inhibitor enzastaurin has shown promising pre-clinical activity in a wide range of tumor cells. In this study, we further delineated its mechanism of action in multiple myeloma (MM) cells and found a novel role of b-catenin in regulating growth and survival of tumor cells. Specifically, inhibition of PKC leads to rapid accumulation of b-catenin by preventing the phosphorylation required for its proteasomal degradation. Microarray analysis and siRNA-mediated gene silencing in MM cells revealed that accumulated b-catenin activates early ER stress signaling via eIF2a, CHOP and p21, leading to immediate growth inhibition. Furthermore, accumulated b-catenin contributes to enzastaurin-induced cell death. Both sequential knock-down of b-catenin, c-Jun, and p73, as well as overexpression of b-catenin or p73 confirmed that accumulated b-catenin triggers c-Jun-dependent induction of p73, thereby conferring MM cell apoptosis. In summary, our data reveal a novel role of b-catenin in ER stress-mediated growth inhibition, and a new pro-apoptotic mechanism triggered by b-catenin upon inhibition of PKC isoforms. Moreover, we identify p73 as a potential novel therapeutic target in MM. Based on these and previous data, enzastaurin is currently under clinical investigation in a variety of hematologic malignancies including MM. Keywords: time course Overall design: MM.1S myeloma cell lines were treated with enzastaurin for 3, 6 or 12 hours. Controls are represented by untreated cells, at the same time points.
Project description:Erguler2013 - Unfolded protein stress response
The model investigates the mechanism by which UPR (unfolded protein response) outcome switches between survival and death.
This model is described in the article:
A mathematical model of the unfolded protein stress response reveals the decision mechanism for recovery, adaptation and apoptosis.
Erguler K, Pieri M, Deltas C.
BMC Syst Biol. 2013 Feb 21;7(1):16.
BACKGROUND: The unfolded protein response (UPR) is a major signalling cascade acting in the quality control ofprotein folding in the endoplasmic reticulum (ER). The cascade is known to play an accessory rolein a range of genetic and environmental disorders including neurodegenerative and cardiovasculardiseases, diabetes and kidney diseases. The three major receptors of the ER stress involved withthe UPR, i.e. IRE1a, PERK and ATF6, signal through a complex web of pathways to convey anappropriate response. The emerging behaviour ranges from adaptive to maladaptive depending on theseverity of unfolded protein accumulation in the ER; however, the decision mechanism for the switchand its timing have so far been poorly understood.
Here, we propose a mechanism by which the UPR outcome switches between survival and death.We compose a mathematical model integrating the three signalling branches, and perform a comprehensivebifurcation analysis to investigate possible responses to stimuli. The analysis reveals threedistinct states of behaviour, low, high and intermediate activity, associated with stress adaptation, tolerance,and the initiation of apoptosis. The decision to adapt or destruct can, therefore, be understoodas a dynamic process where the balance between the stress and the folding capacity of the ER playsa pivotal role in managing the delivery of the most appropriate response. The model demonstratesfor the first time that the UPR is capable of generating oscillations in translation attenuation and theapoptotic signals, and this is supplemented with a Bayesian sensitivity analysis identifying a set ofparameters controlling this behaviour.
This work contributes largely to the understanding of one of the most ubiquitous signalling pathwaysinvolved in protein folding quality control in the metazoan ER. The insights gained have direct consequenceson the management of many UPR-related diseases, revealing, in addition, an extended listof candidate disease modifiers. Demonstration of stress adaptation sheds light to how preconditioningmight be beneficial in manifesting the UPR outcome to prevent untimely apoptosis, and paves the wayto novel approaches for the treatment of many UPR-related conditions.
In the paper, PERKA refers to the amount of phosphorylated PERK monomer. However, it refers to the active complex in the model. The complex with the model parameterization is formed of 4 monomers (n=4). So, the value of PERKA should be multiplied by 4, in order to generate the figures in the paper (eg. Figure 12).
An additional parameter (tmr=10)) is used in the model. This parameter is not mentioned in the paper. The model values of kf(=10) and kr(=1) are not consistent with that of the paper (kf=100, kr=10, in the paper). However, this is corrected by the introduction of "tmr" in the model, which is multiplied with kf and kr to get the resulting values.
The term "tmr" was missing in the kinetic laws of the reactions reu7 and reu8, in the original model. This has been corrected as per the author's request.
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Project description:Development of cirrhosis and hepatocellular carcinoma is main dangerous consequences of Hepatitis B virus (HBV) infection. Although a lot of data accumulated about host's immune response against infected hepatocytes, less is known about direct pathogenic effects of HBV proteins. Here we have investigated pathological outcomes of HBV envelope polypeptides expression in the liver of transgenic mice. Expression of HBV proteins induced endoplasmic reticulum (ER) stress response in hepatocytes. ER stress response included activation of PKR-like ER-localized eukaryotic initiation factor 2α (eIF2α) kinase (PERK) and eIF2α phosphorylation. In young transgenic mice on BALB/c genetic background eIF2α phosphorylation resulted in activation of GADD153/CHOP-dependent apoptosis that led to stronger liver injury and fibrosis compared to transgenic mice on C57BL/6 genetic background. Hepatic stellate cells represented the main collagen-producing cells in the liver of HBV transgenic mice. Further, key regulator of hepatocytes proliferation transcription factor c-Jun was up-regulated and this up-regulation was accompanied by c-Jun N-terminal kinases (JNK) activation in the liver of HBV transgenic mice. Thus, HBV envelope polypeptides induced host genetic background-dependent liver injury and fibrosis, and, more important, stimulated c-Jun expression and activated PERK genetic background-independent creating conditions in the liver that promote cancer cell proliferation and tumour growth. Overall design: Microarray experiments were performed as dual-color hybridizations. In order to compensate specific effects of the dyes and to ensure statistically relevant data analysis, a color-swap dye-reversal was performed.