Downregulation Of Stress Response Genes Research Articles

Caspase-2 protects against ferroptotic cell death

Caspase-2, one of the most evolutionarily conserved members of the caspase family, is an important regulator of the cellular response to oxidative stress. Given that ferroptosis is suppressed by antioxidant defense pathways, such as that involving selenoenzyme glutathione peroxidase 4 (GPX4), we hypothesized that caspase-2 may play a role in regulating ferroptosis. This study provides the first demonstration of an important and unprecedented function of caspase-2 in protecting cancer cells from undergoing ferroptotic cell death. Specifically, we show that depletion of caspase-2 leads to the downregulation of stress response genes including SESN2, HMOX1, SLC7A11, and sensitizes mutant-p53 cancer cells to cell death induced by various ferroptosis-inducing compounds. Importantly, the canonical catalytic activity of caspase-2 is not required for its role and suggests that caspase-2 regulates ferroptosis via non-proteolytic interaction with other proteins. Using an unbiased BioID proteomics screen, we identified novel caspase-2 interacting proteins (including heat shock proteins and co-chaperones) that regulate cellular responses to stress. Finally, we demonstrate that caspase-2 limits chaperone-mediated autophagic degradation of GPX4 to promote the survival of mutant-p53 cancer cells. In conclusion, we document a novel role for caspase-2 as a negative regulator of ferroptosis in cells with mutant p53. Our results provide evidence for a novel function of caspase-2 in cell death regulation and open potential new avenues to exploit ferroptosis in cancer therapy.

Nutrient Starvation Exposure Induced the Down-Regulation of Stress Responsive Genes and Selected Bioactive Metabolic Pathways in Phaeodactylum tricornutum

The microalga Phaeodactylum tricornutum is considered a model diatom. It is the second diatom whose genome was sequenced and the first one genetically engineered. This permits its use as a cell factory for the production of high-value compounds for nutraceutical, cosmeceutical, pharmaceutical, biodiesel, and bioplastic applications. This study is focused on analyzing expression levels of enzymes involved in the synthesis of sulfoglycolipids and monogalactosyldiacylglycerols, compounds known to have anticancer and immunomodulatory activities, and genes coding antioxidant, heat shock and stress-responsive proteins, in various culturing conditions. Our data showed that both nutrient starvation and senescence induced the down-regulation of both sulfoglycolipid and monogalactosyldiacylglycerol synthesis-related genes and stress-responsive genes (compared to the replete condition), suggesting that the control condition, consisting of cells in the exponential phase in replete medium, is the condition with the highest expression of the genes of interest and worth of further bioactivity screening and chemical analyses for drug discovery and biotechnological applications.

RNA-seq analysis reveals a key role of brassinolide-regulated pathways in NaCl-stressed cotton

Brassinolide (BL) alleviates salt injury in cotton seedlings; however, little is known about the molecular mechanisms of this response. In this study, digital gene expression analysis was performed to better understand the regulatory pathways of BL in NaCl-stressed cotton (Gossypium hirsutum L.). Compared with control plants (CK), a total of 1 162 and 7 659 differentially expressed genes (DEGs) were detected in the leaves and roots of NaCl-treated plants, respectively. Most of the DEGs in NaCl-treated plants, compared to CK, were regulated by BL. Moreover, expression patterns of DEGs in BL+NaCl treated plants were similar to those in CK plants; however, the responses of DEGs in the leaves and roots of NaCl-treated plants to BL differed. In the roots, BL-regulated DEGs were involved in protein biosynthesis, whereas in the leaves, BL promoted photosynthesis in NaCl-stressed cotton. BL treatment also significantly increased the overall biomass, chlorophyll a + b content in leaves, and the protein content in roots in NaCl-stressed cotton. The downregulation of stress-responsive genes in BL+NaCl-stressed leaves was also found. These results suggest that BL can alleviate NaCl injury in cotton plants.

Ezrin Inhibition Up-regulates Stress Response Gene Expression

Ezrin is a member of the ERM (ezrin/radixin/moesin) family of proteins that links cortical cytoskeleton to the plasma membrane. High expression of ezrin correlates with poor prognosis and metastasis in osteosarcoma. In this study, to uncover specific cellular responses evoked by ezrin inhibition that can be used as a specific pharmacodynamic marker(s), we profiled global gene expression in osteosarcoma cells after treatment with small molecule ezrin inhibitors, NSC305787 and NSC668394. We identified and validated several up-regulated integrated stress response genes including PTGS2, ATF3, DDIT3, DDIT4, TRIB3, and ATF4 as novel ezrin-regulated transcripts. Analysis of transcriptional response in skin and peripheral blood mononuclear cells from NSC305787-treated mice compared with a control group revealed that, among those genes, the stress gene DDIT4/REDD1 may be used as a surrogate pharmacodynamic marker of ezrin inhibitor compound activity. In addition, we validated the anti-metastatic effects of NSC305787 in reducing the incidence of lung metastasis in a genetically engineered mouse model of osteosarcoma and evaluated the pharmacokinetics of NSC305787 and NSC668394 in mice. In conclusion, our findings suggest that cytoplasmic ezrin, previously considered a dormant and inactive protein, has important functions in regulating gene expression that may result in down-regulation of stress response genes.

Subinhibitory concentrations of antibiotics affect stress and virulence gene expression inListeria monocytogenesand cause enhanced stress sensitivity but do not affect Caco-2 cell invasion

Antibiotics can act as signal molecules and affect bacterial gene expression, physiology and virulence. The purpose of this study was to determine whether subinhibitory antibiotic concentrations alter gene expression and physiology of Listeria monocytogenes. Using an agar-based screening assay with promoter fusions, 14 of 16 antibiotics induced or repressed expression of one or more stress and/or virulence genes. Despite ampicillin-induced up-regulation of PinlA-lacZ expression, Caco-2 cell invasion was not affected. Subinhibitory concentrations of ampicillin and tetracycline caused up- and down-regulation of stress response genes, respectively, but both antibiotics caused increased sensitivity to acid stress. Six combinations of gene-antibiotic were quantified in broth cultures and five of the six resulted in the same expression pattern as the agar-based assay. Antibiotics affect virulence and/or stress gene expression; however, altered expression could not predict changes in phenotypic behaviour. Subinhibitory concentrations of antibiotics led to increased acid sensitivity, and we speculate that this is attributed to changes in cell envelope or reduced σ(B) -dependent gene expression. Although subinhibitory concentrations of antibiotics affect gene expression in L. monocytogenes, the changes did not increase virulence but did enhance the acid sensitivity.

Effects of Bacterial ACC Deaminase onBrassica napusGene Expression

Plants in association with plant growth-promoting rhizobacteria can benefit from lower plant ethylene levels through the action of the bacterial enzyme 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase. This enzyme cleaves the immediate biosynthetic precursor of ethylene, ACC. Ethylene is responsible for many aspects of plant growth and development but, under stressful conditions, it exacerbates stress symptoms. The ACC deaminase-containing bacterium Pseudomonas putida UW4 is a potent plant growth-promoting strain and, as such, was used to elaborate the detailed role of bacterial ACC deaminase in Brassica napus (canola) plant growth promotion. Transcriptional changes in bacterially treated canola plants were investigated with the use of an Arabidopsis thaliana oligonucleotide microarray. A heterologous approach was necessary because there are few tools available at present to measure global expression changes in nonmodel organisms, specifically with the sensitivity of microarrays. The results indicate that the transcription of genes involved in plant hormone regulation, secondary metabolism, and stress response was altered in plants by the presence of the bacterium, whereas the upregulation of genes for auxin response factors and the downregulation of stress response genes was observed only in the presence of bacterial ACC deaminase. These results support the suggestion that there is a direct link between ethylene and the auxin response, which has been suggested from physiological studies, and provide more evidence for the stress-reducing benefits of ACC deaminase-expressing plant growth-promoting bacteria.

Single-Walled Carbon Nanotubes Downregulate Stress-Responsive Genes in Human Respiratory Tract Cells

Carbon nanotubes (CNTs) are currently key promising materials of nanotechnology. However, elucidation of the possible effects of CNTs on the respiratory tract is urgently needed. The present study aimed to clarify the effect of single-walled CNTs (SWCNTs) on the expression of stress-responsive genes, using primary cultured normal human bronchial epithelial (NHBE), diseased HBE (DHBE) cells, and the human carcinoma cell lines A549 and FaDu. Purified SWCNTs were applied at concentrations of 0.1 or 1.0 mg/mL for 6 h, and a polymerase chain reaction (PCR) array was conducted to examine 84 stress-responsive genes. NHBE cell exposure to SWCNTs resulted in global downregulation of genes involved in inflammation, oxidative stress, and apoptosis. Further analysis using DHBE cells and carcinoma cell lines indicated a similar trend, although differences in sensitivity were observed. Downregulation of stress-responsive genes may be involved in the mechanism by which stress response protects against lung injury.

Genome‐wide expression analysis of cells expressing gain of function mutant D374Y‐PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of serum cholesterol. The possibility that PCSK9 also functions in other pathways needs to be addressed. We have transfected HepG2 cells with mutant D374Y-PCSK9 or control vector. Gene expression signatures were determined using the Affymetrix GeneChip technology, and the expression pattern of selected genes was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). Data was normalized and analyzed using a model-based background adjustment for oligonucleotide expression arrays, then filtered based upon expression within treatments group, and subjected to moderated t-statistics. Five hundred twenty transcripts had altered expression levels between D374Y-PCSK9 and control vector. Among the 520 probes on our top list, 312 were found to have an assigned Gene Ontology (GO) term, and 96 were found in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Genome-wide expression profiling revealed that "steroid biosynthesis," "sterol metabolism," and "cholesterol biosynthsis" were affected by D374Y-PCSK9. Also, the GO biological process terms "response to stresss," "response to virus," "response to unfolded protein," and "immune response" were influenced by D374Y-PCSK9. Our results suggest that D374Y-PCSK9 results in up-regulation of genes involved in sterol biosynthesis and down-regulation of stress-response genes and specific inflammation pathways.

Role ofRAS2in Recovery from Chronic Stress: Effect on Yeast Life Span

The replicative life span ofSaccharomyces cerevisiaewas previously shown to be modulated by the homologous signal transducers Ras1p and Ras2p in a reciprocal manner. We have used thermal stress as a life span modulator in order to uncover functional differences between theRASgenes that may contribute to their divergent effects on life span. Chronic exposure of cells throughout life to recurring heat shocks at sublethal temperatures decreased their replicative life span.ras2mutants, however, suffered the largest decrease compared to wild-type andras1mutant cells. The decrease was correlated with a substantial delay in resumption of budding upon recovery from these heat shocks, indicating an impaired renewal of cell cycling. Detailed analysis of gene expression showed that, during recovery,ras2mutants were selectively impaired in down-regulation of stress-responsive genes and up-regulation of growth-promoting genes. Our results suggest that one of the functions ofRAS2in maintaining life span, for whichRAS1does not substitute, is to ensure renewal of growth and cell division after bouts of stress that cells encounter during their life. This activity ofRAS2is effected by the cyclic AMP pathway. Overexpression ofRAS2,but notRAS2ser42which is deficient in the activation of adenylate cyclase, completely reversed the effect of chronic stress on life span. Thus,RAS2is limiting for longevity in the face of chronic stress. SinceRAS2is known to down-regulate stress responses, this demonstrates that for longevity the ability to recover from stress is at least as important as the ability to mount a stress response.