ATF-2 is preferentially activated by stress-activated protein kinases to mediate c-jun induction in response to genotoxic agents

Crosstalk between phytochemicals and inflammatory signaling pathways

Novel bioactive constituents from natural sources are actively being investigated. The phytochemicals in these phenolic compounds are believed to have a variety of beneficial effects on human health. Several phenolic compounds have been found in plants. The antioxidant potential of phenols has been discussed in numerous studies along with their anti-inflammatory effects on pro-inflammatory cytokine, inducible cyclooxygenase-2, and nitric oxide synthase. Through current study, an attempt is made to outline and highlight a wide variety of inflammation-associated signaling pathways that have been modified by several natural compounds. These signaling pathways include nuclear factor-kappa B (NF-кB), activator protein (AP)-1, protein tyrosine kinases (PTKs), mitogen-activated protein kinases (MAPKs), nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factors, tyrosine phosphatidylinositol 3-kinase (PI3K)/AKT, and the ubiquitin-proteasome system. In light of the influence of natural substances on signaling pathways, their impact on the production of inflammatory mediator is highlighted in this review.

Phospho-proteomics identifies a critical role of ATF2 in pseudorabies virus replication

Pseudorabies virus (PRV), an etiological agent of pseudorabies in livestock, has negatively affected the porcine industry all over the world. Epithelial cells are reported as the first site of PRV infection. However, the role of host proteins and its related signaling pathways in PRV replication is largely unclear. In this study, we performed a quantitative phosphoproteomics screening on PRV-infected porcine kidney (PK-15) epithelial cells. Totally 5723 phosphopeptides, corresponding to 2180 proteins, were obtained, and the phosphorylated states of 810 proteins were significantly different in PRV-infected cells compared with mock-infected cells (P ​< ​0.05). GO and KEGG analysis revealed that these differentially expressed phosphorylated proteins were predominantly related to RNA transport and MAPK signaling pathways. Further functional studies of NF-κB, transcription activator factor-2 (ATF2), MAX and SOS genes in MAPK signaling pathway were analyzed using RNA interference (RNAi) knockdown. It showed that only ATF2-knockdown reduces both PRV titer and viral genome copy number. JNK pathway inhibition and CRISPR/Cas9 gene knockout showed that ATF2 was required for the effective replication of PRV, especially during the biogenesis of viral genome DNA. Subsequently, by overexpression of the ATF2 gene and point mutation of the amino acid positions 69/71 of ATF2, it was further demonstrated that the phosphorylation of ATF2 promoted PRV replication. These findings suggest that ATF2 may provide potential therapeutic target for inhibiting PRV infection.

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Phosphoproteomic profiling of PRV-infected PK-15 ​cells with iTRAQ-quantification.

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JNK pathway regulates ATF2 phosphorylation and PRV replication.

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Phosphorylation of ATF2 promotes PRV replication.

A comprehensive coverage insurance for cells: revealing links between ribosome collisions, stress responses and mRNA surveillance

Cells of metazoans respond to internal and external stressors by activating stress response pathways that aim for re-establishing cellular homoeostasis or, if this cannot be achieved, triggering programmed cell death. Problems during translation, arising from defective mRNAs, tRNAs, ribosomes or protein misfolding, can activate stress response pathways as well as mRNA surveillance and ribosome quality control programs. Recently, ribosome collisions have emerged as a central signal for translational stress and shown to elicit different stress responses. Here, we review our current knowledge about the intricate mutual connections between ribosome collisions, stress response pathways and mRNA surveillance. A central factor connecting the sensing of collided ribosomes with degradation of the nascent polypeptides, dissociation of the stalled ribosomes and degradation of the mRNA by no-go or non-stop decay is the E3-ligase ZNF598. We tested whether ZNF598 also plays a role in nonsense-mediated mRNA decay (NMD) but found that it is dispensable for this translation termination-associated mRNA surveillance pathway, which in combination with other recent data argues against stable ribosome stalling at termination codons being the NMD-triggering signal.

Combined Quantitative (Phospho)proteomics and Mass Spectrometry Imaging Reveal Temporal and Spatial Protein Changes in Human Intestinal Ischemia-Reperfusion

Intestinal ischemia–reperfusion (IR) injury is a severe clinical condition, and unraveling its pathophysiology is crucial to improve therapeutic strategies and reduce the high morbidity and mortality rates. Here, we studied the dynamic proteome and phosphoproteome in the human intestine during ischemia and reperfusion, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis to gain quantitative information of thousands of proteins and phosphorylation sites, as well as mass spectrometry imaging (MSI) to obtain spatial information. We identified a significant decrease in abundance of proteins related to intestinal absorption, microvillus, and cell junction, whereas proteins involved in innate immunity, in particular the complement cascade, and extracellular matrix organization increased in abundance after IR. Differentially phosphorylated proteins were involved in RNA splicing events and cytoskeletal and cell junction organization. In addition, our analysis points to mitogen-activated protein kinase (MAPK) and cyclin-dependent kinase (CDK) families to be active kinases during IR. Finally, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) MSI presented peptide alterations in abundance and distribution, which resulted, in combination with Fourier-transform ion cyclotron resonance (FTICR) MSI and LC-MS/MS, in the annotation of proteins related to RNA splicing, the complement cascade, and extracellular matrix organization. This study expanded our understanding of the molecular changes that occur during IR in the human intestine and highlights the value of the complementary use of different MS-based methodologies.

CDK4/6 and MAPK-Crosstalk as Opportunity for Cancer Treatment

Despite the development of targeted therapies and novel inhibitors, cancer remains an undefeated disease. Resistance mechanisms arise quickly and alternative treatment options are urgently required, which may be partially met by drug combinations. Protein kinases as signaling switchboards are frequently deregulated in cancer and signify vulnerable nodes and potential therapeutic targets. We here focus on the cell cycle kinase CDK6 and on the MAPK pathway and on their interplay. We also provide an overview on clinical studies examining the effects of combinational treatments currently explored for several cancer types.

N-3 PUFAs inhibited hepatic ER stress induced by feeding of a high-saturated fat diet accompanied by the expression LOX-1

Excessive consumption of saturated fat leads to non-alcoholic fatty liver disease (NAFLD), which is attenuated by supplementation of n-3 polyunsaturated fatty acids (PUFAs). Endoplasmic reticulum (ER) stress is crucial in the development of NAFLD, but how high-saturated fat diet (HFD) causes ER stress and NAFLD remains unclear. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is involved in hepatic ER stress. We aimed to explore the roles of LOX-1 in HFD-induced ER stress. Male Sprague-Dawley rats were fed an HFD without or with supplementation of fish oil for 16 weeks. The effects of n-3 PUFAs on hepatic ER stress degrees and the expression levels of LOX-1 were examined. Then human L02 hepatoma cells were treated with palmitate or palmitate and DHA to determine the ER stress and LOX-1 expression levels in vitro. After that the expression of LOX-1 in L02 cells was either knocked-down or overexpressed to analyze the roles of LOX-1 in palmitate-induced ER stress. The feeding of HFD induced NAFLD development and ER stress in the liver, and LOX-1 expressing level, which were all reversed by fish oil supplementation. In vitro, DHA treatment reduced the expression of LOX-1, and palmitate-induced ER stress. SiRNA-mediated knock-down of LOX-1 inhibited palmitate-induced ER stress, whereas overexpression of LOX-1 dramatically induced ER stress in L02 cells.LOX-1 is critical for HFD-induced ER stress, and inhibition of its expression under the treatment of n-3 PUFAs could ameliorate HFD-induced NAFLD.

The autophagy protein Ambra1 regulates gene expression by supporting novel transcriptional complexes

Ambra1 is considered an autophagy and trafficking protein with roles in neurogenesis and cancer cell invasion. Here, we report that Ambra1 also localizes to the nucleus of cancer cells, where it has a novel nuclear scaffolding function that controls gene expression. Using biochemical fractionation and proteomics, we found that Ambra1 binds to multiple classes of proteins in the nucleus, including nuclear pore proteins, adaptor proteins such as FAK and Akap8, chromatin-modifying proteins, and transcriptional regulators like Brg1 and Atf2. We identified biologically important genes, such as Angpt1, Tgfb2, Tgfb3, Itga8, and Itgb7, whose transcription is regulated by Ambra1-scaffolded complexes, likely by altering histone modifications and Atf2 activity. Therefore, in addition to its recognized roles in autophagy and trafficking, Ambra1 scaffolds protein complexes at chromatin, regulating transcriptional signaling in the nucleus. This novel function for Ambra1, and the specific genes impacted, may help to explain the wider role of Ambra1 in cancer cell biology.

The activating transcription factor 2: an influencer of cancer progression

In contrast to the continuous increase in survival rates for many cancer entities, colorectal cancer (CRC) and pancreatic cancer are predicted to be ranked among the top 3 cancer-related deaths in the European Union by 2025. Especially, fighting metastasis still constitutes an obstacle to be overcome in CRC and pancreatic cancer. As described by Fearon and Vogelstein, the development of CRC is based on sequential mutations leading to the activation of proto-oncogenes and the inactivation of tumour suppressor genes. In pancreatic cancer, genetic alterations also attribute to tumour development and progression. Recent findings have identified new potentially important transcription factors in CRC, among those the activating transcription factor 2 (ATF2). ATF2 is a basic leucine zipper protein and is involved in physiological and developmental processes, as well as in tumorigenesis. The mutation burden of ATF2 in CRC and pancreatic cancer is rather negligible; however, previous studies in other tumours indicated that ATF2 expression level and subcellular localisation impact tumour progression and patient prognosis. In a tissue- and stimulus-dependent manner, ATF2 is activated by upstream kinases, dimerises and induces target gene expression. Dependent on its dimerisation partner, ATF2 homodimers or heterodimers bind to cAMP-response elements or activator protein 1 consensus motifs. Pioneering work has been performed in melanoma in which the dual role of ATF2 is best understood. Even though there is increasing interest in ATF2 recently, only little is known about its involvement in CRC and pancreatic cancer. In this review, we summarise the current understanding of the underestimated ‘cancer gene chameleon’ ATF2 in apoptosis, epithelial-to-mesenchymal transition and microRNA regulation and highlight its functions in CRC and pancreatic cancer. We further provide a novel ATF2 3D structure with key phosphorylation sites and an updated overview of all so-far available mouse models to study ATF2 in vivo.

P38-β/SAPK-inhibiting and apoptosis-inducing activities of (E)-4-chloro-2-((3-ethoxy-2-hydroxybenzylidene) amino)phenol

The present study has three purposes; first evaluating cytotoxicity of (E)-4-chloro-2-((3-ethoxy-2-hydroxybenzylidene)amino)phenol (ACES), second deciphering ACES-mediated cellular death mechanism, and third estimating ACES-mediated alterations in the expressions of mitogen-activated protein kinase (MAPK) pathway-related genes. Neutral red uptake assay, cell cycle analysis, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) measurements, caspase 3/7 and 9 activations, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were implemented. IC₅₀ values of ACES-treated five cells were around 4-6 µg/mL. However, Caco-2 and Huh-7 cells were found to be twofold resistant and fivefold sensitive with IC₅₀ values of 11 µg/mL and 0.93 µg/mL, respectively. In this study, it was initially reported that ACES exhibits selective cytotoxicity to Huh-7 cells. In addition, ACES induced apoptosis by nuclear fragmentation, MMP disruption, and intracellular ROS elevation in MCF-7 cells. qRT-PCR experiment indicated the expressions of 30 genes including ATF2, CREB1, MYC, NFATC4 (NFAT3), CCNA1, CCNB1, CCND2, CDK2, CDKN1A (p21CIP1), CDKN1C (p57KIP2), CDKN2A (p16INK4a), CDKN2B (p15INK4b), DLK1, NRAS, CDC42, PAK1, MAP4K1 (HPK1), MAP3K3 (MEKK3), MAP2K3 (MEK3), MAP2K6 (MEK6), MOS, MAPK1 (ERK2), MAPK8 (JNK1), MAPK10 (JNK3), MAPK11 (p38-β), LAMTOR3 (MP1), MAPK8IP2 (JIP-1), PRDX6 (AOP2), COL1A1, and HSPA5 (Grp78) were downregulated at least 1.5-fold. Moreover, ACES effectively inhibited expressions of genes that code for elements of p38-β/stress-activated protein kinase (SAPK) pathway. ACES has the potential to be used for the reversal of trastuzumab resistance in breast cancer patients by inhibiting p38/SAPK pathway in MCF-7 cells. Therefore, with the selective cytotoxic, apoptosis-inducing, and p38-β/SAPK-inhibiting activities, ACES can be utilized for developing a novel anticancer drug.

JNK-Dependent cJun Phosphorylation Mitigates TGFβ- and EGF-Induced Pre-Malignant Breast Cancer Cell Invasion by Suppressing AP-1-Mediated Transcriptional Responses

Transforming growth factor-β (TGFβ) has both tumor-suppressive and tumor-promoting effects in breast cancer. These functions are partly mediated through Smads, intracellular transcriptional effectors of TGFβ. Smads form complexes with other DNA-binding transcription factors to elicit cell-type-dependent responses. Previously, we found that the collagen invasion and migration of pre-malignant breast cancer cells in response to TGFβ and epidermal growth factor (EGF) critically depend on multiple Jun and Fos components of the activator protein (AP)-1 transcription factor complex. Here we report that the same process is negatively regulated by Jun N-terminal kinase (JNK)-dependent cJun phosphorylation. This was demonstrated by analysis of phospho-deficient, phospho-mimicking, and dimer-specific cJun mutants, and experiments employing a mutant version of the phosphatase MKP1 that specifically inhibits JNK. Hyper-phosphorylation of cJun by JNK strongly inhibited its ability to induce several Jun/Fos-regulated genes and to promote migration and invasion. These results show that MEK-AP-1 and JNK-phospho-cJun exhibit distinct pro- and anti-invasive functions, respectively, through differential regulation of Smad- and AP-1-dependent TGFβ target genes. Our findings are of importance for personalized cancer therapy, such as for patients suffering from specific types of breast tumors with activated EGF receptor-Ras or inactivated JNK pathways.

ERK1/ATF-2 signaling axis contributes to interleukin-1β-induced MMP-3 expression in dermal fibroblasts

Matrix metalloproteinases (MMPs) play a pivotal role in tissue remodeling by degrading the extracellular matrix (ECM) components. This mechanism is implicated in a variety of physiological and pathological cellular processes including wound healing. One of the key proteins involved in this process is the proinflammatory cytokine interleukin-1β (IL-1β, which induces the expression of MMP-3 mRNA and the secretion of MMP-3 protein by dermal fibroblasts. In this study, we first investigated the contribution of activating transcription factor 2 (ATF-2) to IL-1β-induced MMP-3 expression in dermal fibroblasts. Our results showed that in cells transfected with ATF-2 siRNA or treated with the ATF-2 inhibitor SBI-0087702, IL-1β-induced MMP-3 mRNA expression was reduced. We also demonstrated that IL-1β stimulates the phosphorylation of ATF-2. These observations suggest that ATF-2 plays an important role in IL-1β-induced MMP-3 expression. Next, we investigated the role of MAPK signaling in ATF-2 activation. In cells treated with the extracellular signal-regulated kinase (ERK) inhibitor FR180240, as well as in cells transfected with ERK1 and ERK2 siRNAs, IL-1β-induced MMP-3 mRNA expression was reduced. In addition, we showed that IL-1β induced the phosphorylation of ERK1/2. These observations suggest that ERK1 and ERK2 are involved in IL-1β-induced MMP-3 expression. However, ERK1 and ERK2 do seem to play different roles. While the ERK inhibitor FR180204 inhibited IL-1β-induced ATF-2 phosphorylation, only in cells transfected with ERK1 siRNA, but not ERK2 siRNA, IL-1β-induced ATF-2 phosphorylation was reduced. These findings suggest that the ERK1/ATF-2 signaling axis contributes to IL-1β-induced MMP-3 expression in dermal fibroblasts.

A model of the onset of the senescence associated secretory phenotype after DNA damage induced senescence

Cells and tissues are exposed to stress from numerous sources. Senescence is a protective mechanism that prevents malignant tissue changes and constitutes a fundamental mechanism of aging. It can be accompanied by a senescence associated secretory phenotype (SASP) that causes chronic inflammation. We present a Boolean network model-based gene regulatory network of the SASP, incorporating published gene interaction data. The simulation results describe current biological knowledge. The model predicts different in-silico knockouts that prevent key SASP-mediators, IL-6 and IL-8, from getting activated upon DNA damage. The NF-κB Essential Modulator (NEMO) was the most promising in-silico knockout candidate and we were able to show its importance in the inhibition of IL-6 and IL-8 following DNA-damage in murine dermal fibroblasts in-vitro. We strengthen the speculated regulator function of the NF-κB signaling pathway in the onset and maintenance of the SASP using in-silico and in-vitro approaches. We were able to mechanistically show, that DNA damage mediated SASP triggering of IL-6 and IL-8 is mainly relayed through NF-κB, giving access to possible therapy targets for SASP-accompanied diseases.

Enhancement of Protective Effects of Radix Scutellariae on UVB-induced Photo Damage in Human HaCaT Keratinocytes

Radix Scutellariae (RS) has long been used in the treatment of inflammatory and allergic diseases. Its main flavonoids, baicalin (BG) and wogonoside (WG), can be hydrolyzed into their corresponding aglycones, baicalein (B) and wogonin (W). In this study, we developed a safe and effective method of transforming these glycosides using Peclyve PR. The transformation rate of BG and WG reached 98.5 and 98.1%, respectively, with 10% enzyme at 40 °C for 60 h. Furthermore, we compared the anti-photoaging activity of RS before and after enzyme treatment, as well as their respective main components, in UVB-irradiated HaCaT cells. Results found that enzyme-treated RS (ERS) appeared to be much better at preventing UVB-induced photoaging than RS. ERS significantly inhibited the upregulation of matrix metalloproteinase-1 and IL-6 caused by UVB radiation by inactivating the MAPK/AP-1 and NF-κB/IκB-α signaling pathways. ERS treatment also recovered UVB-induced reduction of procollagen type I by activating the TGF-β/Smad pathway. In addition, ERS exhibited an excellent antioxidant activity, which could increase the expression of cytoprotective antioxidants such as HO-1 and NQ-O1, by facilitating Nrf2 nuclear transfer. These findings demonstrated that the photoprotective effects of RS were significantly improved by enzyme-modified biotransformation.

Anthrax lethal toxin rapidly reduces c-Jun levels by inhibiting c-Jun gene transcription and promoting c-Jun protein degradation

Anthrax is a life-threatening disease caused by infection with Bacillus anthracis, which expresses lethal factor and the receptor-binding protective antigen. These two proteins combine to form anthrax lethal toxin (LT), whose proximal targets are mitogen-activated kinase kinases (MKKs). However, the downstream mediators of LT toxicity remain elusive. Here we report that LT exposure rapidly reduces the levels of c-Jun, a key regulator of cell proliferation and survival. Blockade of proteasome-dependent protein degradation with the 26S proteasome inhibitor MG132 largely restored c-Jun protein levels, suggesting that LT promotes degradation of c-Jun protein. Using the MKK1/2 inhibitor U0126, we further show that MKK1/2-Erk1/2 pathway inactivation similarly reduces c-Jun protein, which was also restored by MG132 pre-exposure. Interestingly, c-Jun protein rebounded to normal levels 4 h following U0126 exposure but not after LT exposure. The restoration of c-Jun in U0126-exposed cells was associated with increased c-Jun mRNA levels and was blocked by inactivation of the JNK1/2 signaling pathway. These results indicate that LT reduces c-Jun both by promoting c-Jun protein degradation via inactivation of MKK1/2-Erk1/2 signaling and by blocking c-Jun gene transcription via inactivation of MKK4-JNK1/2 signaling. In line with the known functions of c-Jun, LT also inhibited cell proliferation. Ectopic expression of LT-resistant MKK2 and MKK4 variants partially restored Erk1/2 and JNK1/2 signaling in LT-exposed cells, enabling the cells to maintain relatively normal c-Jun protein levels and cell proliferation. Taken together, these findings indicate that LT reduces c-Jun protein levels via two distinct mechanisms, thereby inhibiting critical cell functions, including cellular proliferation.

ATF2 partly mediated the expressions of proliferative factors and inhibited pro-inflammatory factors' secretion in arsenite-treated human uroepithelial cells

Inorganic arsenic (iAs) could induce the expression of activating transcription factor-2 (ATF2) in the human urinary bladder epithelial cell line (SV-HUC-1 cells). ATF2, as a member of the bZIP transcription factor family, has been implicated in a transcriptional response leading to cell growth, migration and malignant tumor progression. However, little is known about the effects of ATF2 on proliferative factors in iAs treated human urothelial cells. In this study, ATF2 siRNA was employed to investigate the relationship between ATF2 activation and the expressions of proliferative factors, such as BCL2, cyclin D1, COX-2, MMP1 and PCNA, and pro-inflammatory factors (TNFα, TGFα and IL-8) in SV-HUC-1 cells. The results showed that low concentration arsenite increased the expressions of proliferative factors BCL2, cyclin D1, COX-2, MMP1 and PCNA in SV-HUC-1 cells, and ATF2 siRNA partly decreased the expressions of BCL2, cyclin D1, and COX-2. A neutralizing antibody of IL-8 was used for attenuating the levels of IL-8 and neutralizing antibody of IL-8 did not relieve the expressions of ATF2 and proliferative factors induced by arsenite in SV-HUC-1 cells. In addition, ATF2 knockdown did not decrease the expressions of pro-inflammatory cytokines induced by arsenite in SV-HUC-1 cells, but dramatically increased mRNA expressions of TNFα, TGFα and IL-8 under arsenite and non-arsenite conditions. In conclusion, our present study indicated that ATF2, but not IL-8, played a partial role in the expressions of proliferative factors induced by arsenite in human uroepithelial cells.

Adaptations to High Salt in a Halophilic Protist: Differential Expression and Gene Acquisitions through Duplications and Gene Transfers

The capacity of halophiles to thrive in extreme hypersaline habitats derives partly from the tight regulation of ion homeostasis, the salt-dependent adjustment of plasma membrane fluidity, and the increased capability to manage oxidative stress. Halophilic bacteria, and archaea have been intensively studied, and substantial research has been conducted on halophilic fungi, and the green alga Dunaliella. By contrast, there have been very few investigations of halophiles that are phagotrophic protists, i.e., protozoa. To gather fundamental knowledge about salt adaptation in these organisms, we studied the transcriptome-level response of Halocafeteria seosinensis (Stramenopiles) grown under contrasting salinities. We provided further evolutionary context to our analysis by identifying genes that underwent recent duplications. Genes that were highly responsive to salinity variations were involved in stress response (e.g., chaperones), ion homeostasis (e.g., Na+/H+ transporter), metabolism and transport of lipids (e.g., sterol biosynthetic genes), carbohydrate metabolism (e.g., glycosidases), and signal transduction pathways (e.g., transcription factors). A significantly high proportion (43%) of duplicated genes were also differentially expressed, accentuating the importance of gene expansion in adaptation by H. seosinensis to high salt environments. Furthermore, we found two genes that were lateral acquisitions from bacteria, and were also highly up-regulated and highly expressed at high salt, suggesting that this evolutionary mechanism could also have facilitated adaptation to high salt. We propose that a transition toward high-salt adaptation in the ancestors of H. seosinensis required the acquisition of new genes via duplication, and some lateral gene transfers (LGTs), as well as the alteration of transcriptional programs, leading to increased stress resistance, proper establishment of ion gradients, and modification of cell structure properties like membrane fluidity.

BX-795 inhibits HSV-1 and HSV-2 replication by blocking the JNK/p38 pathways without interfering with PDK1 activity in host cells

BX-795 is an inhibitor of 3-phosphoinositide-dependent kinase 1 (PDK1), but also a potent inhibitor of the IKK-related kinase, TANKbinding kinase 1 (TBK1) and IKKɛ. In this study we attempted to elucidate the molecular mechanism(s) underlying the inhibition of BX-795 on Herpes simplex virus (HSV) replication. HEC-1-A or Vero cells were treated with BX-795 and infected with HSV-1 or HSV-2 for different periods. BX-795 (3.125-25 μmol/L) dose-dependently suppressed HSV-2 replication, and displayed a low cytotoxicity to the host cells. BX-795 treatment dose-dependently suppressed the expression of two HSV immediate-early (IE) genes (ICP0 and ICP27) and the late gene (gD) at 12 h postinfection. HSV-2 infection resulted in the activation of PI3K and Akt in the host cells, and BX-795 treatment inhibited HSV-2-induced Akt phosphorylation and activation. However, the blockage of PI3K/Akt/mTOR with LY294002 and rapamycin did not affect HSV-2 replication. HSV-2 infection increased the phosphorylation of JNK and p38, and reduced ERK phosphorylation at 8 h postinfection in the host cells; BX-795 treatment inhibited HSV-2-induced activation of JNK and p38 MAP kinase as well as the phosphorylation of c-Jun and ATF-2, the downstream targets of JNK and p38 MAP kinase. Furthermore, SB203580 (a p38 inhibitor) or SP600125 (a JNK inhibitor) dose-dependently inhibited the viral replication in the host cells, whereas PD98059 (an ERK inhibitor) was not effective. Moreover, BX-795 blocked PMA-stimulated c-Jun activation as well as HSV-2-mediated c-Jun nuclear translocation. BX-795 dose-dependently inhibited HSV-2, PMA, TNF-α-stimulated AP-1 activation, but not HSV-induced NF-κB activation. Overexpression of p38/JNK attenuated the inhibitory effect of BX-795 on HSV replication. BX-795 completely blocked HSV-2-induced MKK4 phosphorylation, suggesting that BX-795 acting upstream of JNK and p38 MAP kinase. In conclusion, this study identifies the anti-HSV activity of BX-795 and its targeting of the JNK/p38 MAP kinase pathways in host cells.

The Zebrafish Equivalent of Alzheimer's Disease-Associated PRESENILIN Isoform PS2V Regulates Inflammatory and Other Responses to Hypoxic Stress

Dominant mutations in the PRESENILIN genes PSEN1 and PSEN2 cause familial Alzheimer's disease (fAD) that usually shows onset before 65 years of age. In contrast, genetic variation at the PSEN1 and PSEN2 loci does not appear to contribute to risk for the sporadic, late onset form of the disease (sAD), leading to doubts that these genes play a role in the majority of AD cases. However, a truncated isoform of PSEN2, PS2V, is upregulated in sAD brains and is induced by hypoxia and high cholesterol intake. PS2V can increase γ-secretase activity and suppress the unfolded protein response (UPR), but detailed analysis of its function has been hindered by lack of a suitable, genetically manipulable animal model since mice and rats lack this PRESENILIN isoform. We recently showed that zebrafish possess an isoform, PS1IV, that is cognate to human PS2V. Using an antisense morpholino oligonucleotide, we can block specifically the induction of PS1IV that normally occurs under hypoxia. Here, we exploit this ability to identify gene regulatory networks that are modulated by PS1IV. When PS1IV is absent under hypoxia-like conditions, we observe changes in expression of genes controlling inflammation (particularly sAD-associated IL1B and CCR5), vascular development, the UPR, protein synthesis, calcium homeostasis, catecholamine biosynthesis, TOR signaling, and cell proliferation. Our results imply an important role for PS2V in sAD as a component of a pathological mechanism that includes hypoxia/oxidative stress and support investigation of the role of PS2V in other diseases, including schizophrenia, when these are implicated in the pathology.

ATF2 translation is induced under chemotherapeutic drug-mediated cellular stress via an IRES-dependent mechanism in human hepatic cancer Bel7402 cells

Activating transcription factor (ATF) 2 is a member of the ATF/cyclic AMP-responsive element binding protein family, which exhibits both oncogenic and tumor-suppressor functions. In our preliminary experiments, it was observed that the expression of the ATF2 protein was induced following treatment with adriamycin (ADR) and paclitaxel (PTX), which may be regulated by internal ribosome entry segment (IRES)-mediated translation. By constructing a bicistronic vector containing the ATF2 5'-untranslated region (UTR), it was demonstrated that the ATF2 5'-UTR contains an IRES and maps a 30-nucleotide (nt) sequence (from nt 299 to nt ~269), which was essential for the IRES activity. The ATF2 IRES activity exhibited significant variation in different cell lines. In addition, it was observed that ADR and PTX also induced ATF2 IRES activity in Bel7402 cells. The present study has demonstrated that ATF2 translation is initiated via IRES, which is upregulated by ADR and PTX, thus suggesting that the regulation of the IRES-dependent translation of ATF2 may be involved in effecting the cancer cell response to chemotherapeutic drugs-mediated cellular stress.

A Protective Mechanism of Visible Red Light in Normal Human Dermal Fibroblasts: Enhancement of GADD45A-Mediated DNA Repair Activity

The phototherapeutic effects of visible red light on skin have been extensively investigated, but the underlying biological mechanisms remain poorly understood. We aimed to elucidate the protective mechanism of visible red light in terms of DNA repair of UV-induced oxidative damage in normal human dermal fibroblasts. The protective effect of visible red light on UV-induced DNA damage was identified by several assays in both two-dimensional and three-dimensional cell culture systems. With regard to the protective mechanism of visible red light, our data showed alterations in base excision repair mediated by growth arrest and DNA damage inducible, alpha (GADD45A). We also observed an enhancement of the physical activity of GADD45A and apurinic/apyrimidinic endonuclease 1 (APE1) by visible red light. Moreover, UV-induced DNA damages were diminished by visible red light in an APE1-dependent manner. On the basis of the decrease in GADD45A-APE1 interaction in the activating transcription factor-2 (ATF2)-knockdown system, we suggest a role for ATF2 modulation in GADD45A-mediated DNA repair upon visible red light exposure. Thus, the enhancement of GADD45A-mediated base excision repair modulated by ATF2 might be a potential protective mechanism of visible red light.

The Role of Interleukin-1 in Inflammatory and Malignant Human Skin Diseases and the Rationale for Targeting Interleukin-1 Alpha

Inflammation plays a major role in the induction and progression of several skin diseases. Overexpression of the major epidermal proinflammatory cytokines interleukin (IL) 1 alpha (IL-1α) and 1 beta (IL-1β) is positively correlated with symptom exacerbation and disease progression in psoriasis, atopic dermatitis, neutrophilic dermatoses, skin phototoxicity, and skin cancer. IL-1β and the interleukin-1 receptor I (IL-1RI) have been used as a therapeutic target for some autoinflammatory skin diseases; yet, their system-wide effects limit their clinical usage. Based on the local effects of extracellular IL-1α and its precursor, pro-IL-1α, we hypothesize that this isoform is a promising drug target for the treatment and prevention of many skin diseases. This review provides an overview on IL-1α and IL-β functions, and their contribution to inflammatory and malignant skin diseases. We also discuss the current treatment regimens, and ongoing clinical trials, demonstrating the potential of targeting IL-1α, and not IL-1β, as a more effective strategy to prevent or treat the onset and progression of various skin diseases.

Tiron Inhibits UVB-Induced AP-1 Binding Sites Transcriptional Activation on MMP-1 and MMP-3 Promoters by MAPK Signaling Pathway in Human Dermal Fibroblasts

Recent research found that Tiron was an effective antioxidant that could act as the intracellular reactive oxygen species (ROS) scavenger or alleviate the acute toxic metal overload in vivo. In this study, we investigated the inhibitory effect of Tiron on matrix metalloproteinase (MMP)-1 and MMP-3 expression in human dermal fibroblast cells. Western blot and ELISA analysis revealed that Tiron inhibited ultraviolet B (UVB)-induced protein expression of MMP-1 and MMP-3. Real-time quantitative PCR confirmed that Tiron could inhibit UVB-induced mRNA expression of MMP-1 and MMP-3. Furthermore, Tiron significantly blocked UVB-induced activation of the MAPK signaling pathway and activator protein (AP)-1 in the downstream of this transduction pathway in fibroblasts. Through the AP-1 binding site mutation, it was found that Tiron could inhibit AP-1-induced upregulation of MMP-1 and MMP-3 expression through blocking AP-1 binding to the AP-1 binding sites in the MMP-1 and MMP-3 promoter region. In conclusion, Tiron may be a novel antioxidant for preventing and treating skin photoaging UV-induced.

Increased SPHK2 Transcription of Human Colon Cancer Cells in Serum-Depleted Culture: The Involvement of CREB Transcription Factor

Sphingosine kinases (SPHK) are important to determine cells' fate by producing sphingosine 1-phosphate. Reportedly, exogenous SPHK2 overexpression induces cell cycle arrest or cell death. However, the regulatory mechanism of SPHK2 expression has not been fully elucidated. Here, we analyzed this issue using human colon cancer cell lines under various stress conditions. Serum depletion (FCS(-)) but not hypoxia and glucose depletion increased mRNA, protein and enzyme activity of SPHK2 but not SPHK1. In HCT116 cells mostly used, SPHK2 activity was predominant over SPHK1, and serum depletion increased both nuclear and cytoplasmic SPHK2 activity. Based on previous reports analyzing cellular response after serum depletion, the temporal changes of intracellular signaling molecules and candidate transcription factors for SPHK2 were examined using serum-depleted HCT116 cells, and performed transfection experiments with siRNA or cDNA of candidate transcription factors. Results showed that the rapid and transient JNK activation followed by CREB activation was the major regulator of increased SPHK2 transcription in FCS(-) culture. EMSA and ChIP assay confirmed the direct binding of activated CREB to the CREB binding site of 5' SPHK2 promoter region. Colon cancer cells examined continued to grow in FCS(-) culture, although mildly, while hypoxia and glucose depletion suppressed cell proliferation or induced cell death, suggesting the different role of SPHK2 in different stress conditions. Because of the unique relationship observed after serum depletion, we examined effects of siRNA for SPHK2, and found the role of SPHK2 as a growth or survival factor but not a cell proliferation inhibitor in FCS(-) culture.

Syndecan4 coordinates Wnt/JNK and BMP signaling to regulate foregut progenitor development

Temporally and spatially dynamic Wnt and BMP signals are essential to pattern foregut endoderm progenitors that give rise to the liver, pancreas and lungs, but how these two signaling pathways are coordinated in the extracellular space is unknown. Here we identify the transmembrane heparan sulphate proteoglycan Syndecan-4 (Sdc4), as a key regulator of both non-canonical Wnt and BMP signaling in the Xenopus foregut. Foregut-specific Sdc4 depletion results in a disrupted Fibronectin (Fn1) matrix, reduced cell adhesion, and failure to maintain foregut gene expression ultimately leading to foregut organ hypoplasia. Sdc4 is required to maintain robust Wnt/JNK and BMP/Smad1 signaling in the hhex+ foregut progenitors. Pathway analysis suggests that Sdc4 functionally interacts with Fzd7 to promote Wnt/JNK signaling, which maintains foregut identity and cell adhesion. In addition, the Sdc4 ectodomain is required to support Fn1 matrix assembly, which is essential for the robust BMP signaling that promotes foregut gene expression. This work sheds lights on how the extracellular matrix can coordinate different signaling pathways during organogenesis.

Leupaxin stimulates adhesion and migration of prostate cancer cells through modulation of the phosphorylation status of the actin-binding protein caldesmon

The focal adhesion protein leupaxin (LPXN) is overexpressed in a subset of prostate cancers (PCa) and is involved in the progression of PCa. In the present study, we analyzed the LPXN-mediated adhesive and cytoskeletal changes during PCa progression. We identified an interaction between the actin-binding protein caldesmon (CaD) and LPXN and this interaction is increased during PCa cell migration. Furthermore, knockdown of LPXN did not affect CaD expression but reduced CaD phosphorylation. This is known to destabilize the affinity of CaD to F-actin, leading to dynamic cell structures that enable cell motility. Thus, downregulation of CaD increased migration and invasion of PCa cells. To identify the kinase responsible for the LPXN-mediated phosphorylation of CaD, we used data from an antibody array, which showed decreased expression of TGF-beta-activated kinase 1 (TAK1) after LPXN knockdown in PC-3 PCa cells. Subsequent analyses of the downstream kinases revealed the extracellular signal-regulated kinase (ERK) as an interaction partner of LPXN that facilitates CaD phosphorylation during LPXN-mediated PCa cell migration. In conclusion, we demonstrate that LPXN directly influences cytoskeletal dynamics via interaction with the actin-binding protein CaD and regulates CaD phosphorylation by recruiting ERK to highly dynamic structures within PCa cells.

JNK-mediated activation of ATF2 contributes to dopaminergic neurodegeneration in the MPTP mouse model of Parkinson's disease

The c-Jun N-terminal kinase (JNK)/c-Jun pathway is a known critical regulator of dopaminergic neuronal death in Parkinson's disease (PD) and is considered a potential target for neuroprotective therapy. However, whether JNK is activated within dopaminergic neurons remains controversial, and whether JNK acts through downstream effectors other than c-Jun to promote dopaminergic neuronal death remains unclear. In this study, we confirm that JNK but not p38 is activated in dopaminergic neurons after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxication. Furthermore, within the dopaminergic neurons of the substantia nigra in MPTP-treated mice, JNK2/3 phosphorylates threonine 69 (Thr69) of Activating transcription factor-2 (ATF2), a transcription factor of the ATF/CREB family, whereas the phosphorylation of Thr71 is constitutive and remains unchanged. The increased phosphorylation of ATF2 on Thr69 by JNK in the MPTP mouse model suggests a functional relationship between the transcriptional activation of ATF2 and dopaminergic neuron death. By using dopaminergic neuron-specific conditional ATF2 mutant mice, we found that either partial or complete deletion of the ATF2 DNA-binding domain in dopaminergic neurons markedly alleviates the MPTP-induced dopaminergic neurodegeneration, indicating that the activation of ATF2 plays a detrimental role in neuropathogenesis in PD. Taken together, our findings demonstrate that JNK-mediated ATF2 activation contributes to dopaminergic neuronal death in an MPTP model of PD.

Proteolysis of MDA5 and IPS-1 is not required for inhibition of the type I IFN response by poliovirus

BACKGROUND

The type I interferon (IFN) response is a critical component of the innate immune response to infection by RNA viruses and is initiated via recognition of viral nucleic acids by RIG-like receptors (RLR). Engagement of these receptors in the cytoplasm initiates a signal transduction pathway leading to activation of the transcription factors NF-κB, ATF-2 and IRF-3 that coordinately upregulate transcription of type I IFN genes, such as that encoding IFN-β. In this study the impact of poliovirus infection on the type I interferon response has been examined.

METHODS

The type I IFN response was assessed by measuring IFN-β mRNA levels using qRT-PCR and normalizing to levels of β-actin mRNA. The status of host factors involved in activation of the type I IFN response was examined by immunoblot, immunofluorescence microcopy and qRT-PCR.

RESULTS

The results show that poliovirus infection results in induction of very low levels of IFN-β mRNA despite clear activation of NF-κB and ATF-2. In contrast, analysis of IRF-3 revealed no transcriptional induction of an IRF-3-responsive promoter or homodimerization of IRF-3 indicating it is not activated in poliovirus-infected cells. Exposure of poliovirus-infected cells to poly(I:C) results in lower levels of IFN-β mRNA synthesis and IRF-3 activation compared to mock-infected cells. Analysis of MDA-5 and IPS-1 revealed that these components of the RLR pathway were largely intact at times when the type I IFN response was suppressed.

CONCLUSIONS

Collectively, these results demonstrate that poliovirus infection actively suppresses the host type I interferon response by blocking activation of IRF-3 and suggests that this is not mediated by cleavage of MDA-5 or IPS-1.

Biomarkers of head and neck cancer, tools or a gordian knot?

Head and neck tumors comprise a wide spectrum of heterogeneous neoplasms for which biomarkers are needed to aid in earlier diagnosis, risk assessment and therapy response. Personalized medicine based on predictive markers linked to drug response, it is hoped, will lead to improvements in outcomes and avoidance of unnecessary treatment in carcinoma of the head and neck. Because of the heterogeneity of head and neck tumors, the integration of multiple selected markers in association with the histopathologic features is advocated for risk assessment. Validation of each biomarker in the context of clinical trials will be required before a specific marker can be incorporated into daily practice. Furthermore, we will give evidence that some proteins implicated in cell-cell interaction, such as CD44 may be involved in the multiple mechanism of the development and progression of laryngeal lesions and may help to predict the risk of transformation of the benign or precancerous lesions to cancer.

Deoxycholic acid inhibited proliferation and induced apoptosis and necrosis by regulating the activity of transcription factors in rat pancreatic acinar cell line AR42J

The objective of this study is to investigate the effect of deoxycholic acid (DCA) on rat pancreatic acinar cell line AR42J and the functional mechanisms of DCA on AR42J cells. AR42J cells were treated with various concentrations of DCA for 24 h and also treated with 0.4 mmol/L DCA for multiple times, and then, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to detect the AR42J cell survival rate. Flow cytometric was used to detect the cell apoptosis and necrosis in AR42J cells treated with 0.4 mmol/L and 0.8 mmol/L DCA. The cells treated with phosphate buffer saline (PBS) were served as control. In addition, the DNA-binding activity assays of transcription factors (TFs) in nuclear proteins of cells treated with DCA were determined using Panomics Procarta Transcription Factor Assay Kit. The relative survival rates were markedly decreased (P < 0.05) in a dose- and time-dependent manner. Compared with control group, the cell apoptosis and necrosis ratio were both significantly elevated in 0.4 mmol/L DCA and 0.8 mmol/L DCA groups (P < 0.01). A significant increase (P < 0.05) in the activity of transcription factor 2 (ATF2), interferon-stimulated response element (ISRE), NKX-2.5, androgen receptor (AR), p53, and hypoxia-inducible factor-1 (HIF-1) was observed, and the activity of peroxisome proliferator-activated receptor (PPAR), activator protein 1 (AP1), and E2F1 was reduced (P < 0.05). In conclusion, DCA inhibited proliferation and induced apoptosis and necrosis in AR42J cells. The expression changes of related genes regulated by TFs might be the molecular mechanism of AR42J cell injury.

Biliverdin reductase isozymes in metabolism

The biliverdin reductase (BVR) isozymes BVRA and BVRB are cell surface membrane receptors with pleiotropic functions. This review compares, for the first time, the structural and functional differences between the isozymes. They reduce biliverdin, a byproduct of heme catabolism, to bilirubin, display kinase activity, and BVRA, but not BVRB, can act as a transcription factor. The binding motifs present in the BVR isozymes allow a wide range of interactions with components of metabolically important signaling pathways such as the insulin receptor kinase cascades, protein kinases (PKs), and inflammatory mediators. In addition, serum bilirubin levels have been negatively associated with abdominal obesity and hypertriglyceridemia. We discuss the roles of the BVR isozymes in metabolism and their potential as therapeutic targets.

Cdk1-mediated phosphorylation of human ATF7 at Thr-51 and Thr-53 promotes cell-cycle progression into M phase

Activating transcription factor 2 (ATF2) and its homolog ATF7 are phosphorylated at Thr-69/Thr-71 and at Thr-51/Thr-53, respectively, by stress-activated MAPKs regulating their transcriptional functions in G1 and S phases. However, little is known about the role of ATF2 and ATF7 in G2/M phase. Here, we show that Cdk1-cyclin B1 phosphorylates ATF2 at Thr-69/Thr-71 and ATF7 at Thr-51/Thr-53 from early prophase to anaphase in the absence of any stress stimulation. Knockdown of ATF2 or ATF7 decreases the rate of cell proliferation and the number of cells in M-phase. In particular, the knockdown of ATF7 severely inhibits cell proliferation and G2/M progression. The inducible expression of a mitotically nonphosphorylatable version of ATF7 inhibits G2/M progression despite the presence of endogenous ATF7. We also show that mitotic phosphorylation of ATF7 promotes the activation of Aurora kinases, which are key enzymes for early mitotic events. These results suggest that the Cdk1-mediated phosphorylation of ATF7 facilitates G2/M progression, at least in part, by enabling Aurora signaling.

Characterization of ATF2 in Rel/NFκB oncogenesis reveals its role in the regulation of Ras signaling

The v-Rel oncoprotein is the acutely transforming member of the Rel/NFκB family of transcription factors. v-Rel transforms cells through the inappropriate activation and suppression of genes normally regulated by cellular Rel/NFκB family members. We have recently demonstrated that activation of Ha-Ras by v-Rel contributes to transformation. Characterization of AP-1 family members in v-Rel-mediated transformation revealed ectopic expression of ATF2 inhibited transformation by blocking Ha-Ras activity. This lack of Ha-Ras activity prevented downstream activation of the Raf-MEK-ERK pathway, a critical pathway for v-Rel-mediated transformation. Microarray analysis of cells treated with an inhibitor to the ERK pathway revealed a relatively small number of genes that are specifically regulated by ERK activity in cells expressing v-Rel. These studies suggest the main contribution of ERK activity is to temper the expression of genes in v-Rel transformed cells. The mechanism by which ATF2 regulates Ras-Raf-MEK-ERK signaling appears to be a context dependent event. The ectopic expression of ATF2 in cells that are not expressing v-Rel results in the activation of Ha-Ras. However, activation of downstream Raf-MEK-ERK signaling pathway is blocked, likely through the recruitment of inhibitory 14-3-3 proteins to c-Raf. These results suggest a diverse role for ATF2 in the regulation of the Ras-Raf-MEK-ERK pathway.

NANOG upregulates c-Jun oncogene expression through binding the c-Jun promoter

NANOG plays important roles in neoplastic processes. However, the molecular mechanism of NANOG in tumorigenesis remains to be elucidated. In this report, we demonstrated that forced expression of NANOG in 293 cells and cancer cells led to increased c-Jun expression, whereas downregulation of endogenous NANOG significantly reduced c-Jun expression in cancer cells. Dual luciferase reporter assays demonstrated that NANOG binds the c-Jun proximal promoter and transactivates the c-Jun gene. An ATTA consensus motif between the -160 and -268 region of the c-Jun promoter was identified as the NANOG-responsive element. Electromobility shift assay and chromatin immunoprecipitation results confirmed the direct binding of NANOG protein to the c-Jun promoter in vitro and in vivo. NANOG directly bound c-Jun protein as shown by GST pulldown and immunoprecipitation assays. Taking these findings together, we conclude that c-Jun is a direct target gene of NANOG and that c-Jun protein may be a novel co-activator of NANOG in cancer cells. We suggest the possibility that NANOG may play a significant role in carcinogenesis via its activation of c-Jun expression.

Phosphorylation of activating transcription factor-2 (ATF-2) within the activation domain is a key determinant of sensitivity to tamoxifen in breast cancer

Activating transcription factor-2 (ATF-2) has been implicated as a tumour suppressor in breast cancer (BC). c-JUN N-terminal kinase (JNK) and p38 MAPK phosphorylate ATF-2 within the activation domain (AD), which is required for its transcriptional activity. To date, the role of ATF-2 in determining response to endocrine therapy has not been explored. Effects of ATF-2 loss in the oestrogen receptor (ER)-positive luminal BC cell line MCF7 were explored, as well as its role in response to tamoxifen treatment. Genome-wide chromatin binding patterns of ATF-2 when phosphorylated within the AD in MCF-7 cells were determined using ChIP-seq. The expression of ATF-2 and phosphorylated ATF-2 (pATF-2-Thr71) was determined in a series of 1,650 BC patients and correlated with clinico-pathological features and clinical outcome. Loss of ATF-2 diminished the growth-inhibitory effects of tamoxifen, while tamoxifen treatment induced ATF-2 phosphorylation within the AD, to regulate the expression of a set of 227 genes for proximal phospho-ATF-2 binding, involved in cell development, assembly and survival. Low expression of both ATF-2 and pATF-2-Thr71 was significantly associated with aggressive pathological features. Furthermore, pATF-2 was associated with both p-p38 and pJNK1/2 (< 0.0001). While expression of ATF-2 is not associated with outcome, pATF-2 is associated with longer disease-free (p = 0.002) and BC-specific survival in patients exposed to tamoxifen (p = 0.01). Furthermore, multivariate analysis confirmed pATF-2-Thr71 as an independent prognostic factor. ATF-2 is important for modulating the effect of tamoxifen and phosphorylation of ATF-2 within the AD at Thr71 predicts for improved outcome for ER-positive BC receiving tamoxifen.

Differential roles of ATF-2 in survival and DNA repair contributing to radioresistance induced by autocrine soluble factors in A549 lung cancer cells

Radioresistance is one of the obstacles to the effective radiotherapy for non-small cell lung cancer. Soluble factors in the tumour microenvironment are often implicated in radioresistance but the underpinning mechanism(s) remain largely elusive. We herein studied the wholesome effect of autocrine cytokines and growth factors in the form of self-conditioned medium (CM) on the radiosensitivity of A549 cells. A549 cells grown in CM exhibited radioresistance which was associated with increased survival and DNA repair. CM induced pro-survival pathways through increased intracellular cAMP and phosphorylation of JNK and p38. Downstream to JNK/p38 signalling, ATF-2 phosphorylated at Thr69/71 was accompanied with its increased transcriptional activity in CM treated cells. Pre-treatment with cAMP inhibitor and silencing of ATF-2 abrogated the CM-induced survival. Interestingly, in cells treated with CM followed by radiation, ATF-2 was found to be switched over from transcription factor to DNA damage response protein. In CM treated cells, after γ-radiation p-ATF-2(Thr69/71) and subsequently the transcriptional activity of ATF-2 were declined with simultaneous rise in p-ATF-2(Ser490/498). Immunoprecipitation/immunoblotting and inhibitor studies showed that phosphorylation of ATF-2 at Ser490/498 was mediated by ATM. Moreover, p-ATF-2(Ser490/498) was found to be co-localised with γ-H2AX in DNA repair foci in CM-treated cells. The DNA repair activity of ATF-2 was assisted with higher activity MRN complex in cells grown in CM. Our study revealed that, autocrine soluble factors regulate dual but differential role of ATF-2 as a transcription factor or DNA repair protein, which collectively culminate in radioresistance of A549 cells.

Nuclear receptor LRH-1/NR5A2 is required and targetable for liver endoplasmic reticulum stress resolution

Chronic endoplasmic reticulum (ER) stress results in toxicity that contributes to multiple human disorders. We report a stress resolution pathway initiated by the nuclear receptor LRH-1 that is independent of known unfolded protein response (UPR) pathways. Like mice lacking primary UPR components, hepatic Lrh-1-null mice cannot resolve ER stress, despite a functional UPR. In response to ER stress, LRH-1 induces expression of the kinase Plk3, which phosphorylates and activates the transcription factor ATF2. Plk3-null mice also cannot resolve ER stress, and restoring Plk3 expression in Lrh-1-null cells rescues ER stress resolution. Reduced or heightened ATF2 activity also sensitizes or desensitizes cells to ER stress, respectively. LRH-1 agonist treatment increases ER stress resistance and decreases cell death. We conclude that LRH-1 initiates a novel pathway of ER stress resolution that is independent of the UPR, yet equivalently required. Targeting LRH-1 may be beneficial in human disorders associated with chronic ER stress.

DOI:http://dx.doi.org/10.7554/eLife.01694.001

A protein can only work properly if it has been folded into the correct shape. However, it is estimated that about one third of new proteins have the wrong shape. This is a major challenge for cells because misfolded proteins are often toxic, and cause many neurodegenerative and metabolic disorders.

In eukaryotic cells, most protein folding takes place inside a part of the cell called the endoplasmic reticulum (ER). If an incorrectly folded protein is detected, it is prevented from leaving the ER until it is refolded correctly, or destroyed. If too many proteins are misfolded, a process called the unfolded protein response helps the cell to cope with this ‘ER stress’ by expanding the ER and producing more of the molecules that assist protein folding. If this does not relieve the ER stress, the cell self-destructs. Neighboring cells then have to increase protein production to compensate for what would have been produced by the dead cell, thereby increasing the chance that they will also experience ER stress.

Activation of a protein called LRH-1 (short for liver receptor homolog-1) that is produced in the liver, pancreas and intestine can relieve the symptoms of the various metabolic diseases that are associated with chronic ER stress, including type II diabetes and fatty liver disease. However, researchers have been puzzled by the fact that although LRH-1 performs many different roles, its molecular structure provides few clues as to how it can do this.

Mamrosh et al. now confirm the speculated link between LRH-1 and ER stress relief in mice. LRH-1 triggers a previously unknown pathway that can relieve ER stress and is completely independent of the unfolded protein response. Targeting LRH-1 with certain chemical compounds alters its activity, suggesting that drug treatments could be developed to relieve ER stress. As similar targets for drugs have not been found in the unfolded protein response, the discovery of the LRH-1 pathway could lead to new approaches to the treatment of the diseases that result from ER stress.

DOI:http://dx.doi.org/10.7554/eLife.01694.002

Modulation of the response of prostate cancer cell lines to cisplatin treatment using small interfering RNA

Cisplatin is one of the most effective and widely used chemotherapeutic agents against several types of human cancers. However, the underlying mechanisms of action are not fully understood. We aimed to investigate the possible molecular mechanism(s) of acquired chemoresistance observed in prostate cancer cells treated with cisplatin. Human LNCaP cells (bearing wild-type p53) and PC-3 cells (lacking p53) were used. The expression levels of protein were determined by western blotting, and the mRNA levels were determined by reverse transcription-polymerase chain reaction (RT-PCR). Cell viability was measured by MTT assay, and the transcriptional effect of small interfering RNA (siRNA) was measured by luciferase reporter gene. We showed that cisplatin treatment increased JNK-1 and JNK-2 activity and expression in both LNCaP and PC-3 cells. In addition, the knockdown of JNK-1 expression by siRNA-JNK-1 or siRNA-JNK-2 significantly impaired the upregulation of AP-1 luciferase reporter gene, but failed to decrease the levels of AP-1 reporter gene expression induced by TPA treatment. Our observations indicate that JNK-1 and JNK-2 may be involved in the chemoresistance observed in prostate cancer cells treated with cisplatin and that blocking the stimulation of Jun kinase (JNK) signaling may be important for regulating the susceptibility to cisplatin of prostate cancer.

Comparative proteomic analysis of peritoneal dialysate from chronic glomerulonephritis patients

Peritoneal dialysis (PD) frequently contributes to peritoneal damage which cannot be easily identified without invasive techniques, implying the urgent need for biomarkers and revealing mechanisms. Chronic glomerulonephritis (CGN) is one of the leading causes of receiving dialysis treatment. Here, we attempted to analyze the peritoneal dialysate collected from CGN patients when they receive continuous ambulatory peritoneal dialysis (CAPD) treatment for the first time and after a year to reveal the protein changes that resulted from PD. Proteins were displayed by two-dimensional gel electrophoresis (2DE). Altered gel spots were digested followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis for protein identification. Eight proteins were found to have differential expression levels between two groups. Their differential expressions were validated by Western blots in other sets of peritoneal dialysates. Proteins identified with higher levels in the first-time dialysate suggested their dominant appearance in CGN patients, while those that showed higher levels in peritoneal dialysate collected after one year may result from initial peritoneal inflammation or changes in the permeability of the peritoneum to middle-sized proteins. All the identified proteins may provide a perceptiveness of peritoneal changes caused by PD and may function as potential biomarkers or drug targets.

Oxidative stress and MAPK involved into ATF2 expression in immortalized human urothelial cells treated by arsenic

ATF2 is a subfamily member of AP-1 and has an important role in cellular stress responses. ATF2 has been implicated in a transcriptional response leading to cell migration and malignant tumor progression. However, little is known about the effect of arsenic on expression of ATF2 and regulatory pathways in human urothelial cells. In this study, ATF2 expression was measured in NaAsO(2)-treated human uroepithelial cell line (SV-HUC-1) with 1, 2, 4, 8 and 10 μM concentrations in order to provide some basis data for the study on mechanism of bladder cancer induced by arsenic. We found that ATF2 expression levels at 2, 4, 8 and 10 μM arsenic-treated cells were significantly higher than those of control cells, and the strongest expression occurred in 4 μM NaAsO(2)-treated cells. Antioxidants (melatonin) and JNK or p38 inhibitors decreased significantly arsenic-induced ATF2 expression. Taken together, these data indicated that the increasing of ATF2 expression is mediated via oxidative stress induced by arsenic in SV-HUC-1 cells, and JNK or p38 rather than ERK is responsible for arsenic-induced ATF2 expression. ROS were also involved in arsenic induced the activation of JNK and p38 MAPK signaling pathway.

Soluble ST2 is regulated by p75 neurotrophin receptor and predicts mortality in diabetic patients with critical limb ischemia

OBJECTIVE

The p75 neurotrophin receptor (p75(NTR)) contributes to diabetes mellitus-induced defective postischemic neovascularization. The interleukin-33 receptor ST2 is expressed as transmembrane (ST2L) and soluble (sST2) isoforms. Here, we studied the following: (1) the impact of p75(NTR) in the healing of ischemic and diabetic calf wounds; (2) the link between p75(NTR) and ST2; and (3) circulating sST2 levels in critical limb ischemia (CLI) patients.

METHODS AND RESULTS

Diabetes mellitus was induced in p75(NTR) knockout (p75KO) mice and wild-type (WT) littermates by streptozotocin. Diabetic and nondiabetic p75KO and WT mice received left limb ischemia induction and a full-thickness wound on the ipsilateral calf. Diabetes mellitus impaired wound closure and angiogenesis and increased ST2 expression in WT, but not in p75KO wounds. In cultured endothelial cells, p75(NTR) promoted ST2 (both isoforms) expression through p38(MAPK)/activating transcription factor 2 pathway activation. Next, sST2 was measured in the serum of patients with CLI undergoing either revascularization or limb amputation and in the 2 nondiabetic groups (with CLI or nonischemic individuals). Serum sST2 increased in diabetic patients with CLI and was directly associated with higher mortality at 1 year from revascularization.

CONCLUSIONS

p75(NTR) inhibits the healing of ischemic lower limb wounds in diabetes mellitus and promotes ST2 expression. Circulating sST2 predicts mortality in diabetic CLI patients.

Effects of heavy metals on mitogen-activated protein kinase pathways

The signaling pathways leading to cellular protection or cell death following exposure to heavy metals have not been fully clarified. Mitogen-activated protein kinases (MAPKs), i.e., extracellular signal-regulated protein kinase (ERK), c-Jun NH(2)-terminal kinase (JNK) and p38 MAPK transmit extracellular signals into the nucleus, and have been shown to participate in a diverse array of cellular functions such as cell growth, differentiation and apoptosis. Treatment with cadmium, inorganic mercury or tributyltin can activate ERK, JNK and p38 MAPK, and induces the expression of c-fos and c-jun genes prior to the development of apoptosis. However, the members of the MAPK family appear to be differentially activated depending on the heavy metal and the cell type exposed. Consequently, various cellular responses may be caused by the distinct pattern of MAPKs activation. MAPKs may be one of the important cellular signal transduction pathways affected by various environmental pollutants, including heavy metals.