Stats: multifaceted regulators of transcription

Methamphetamine facilitates HIV infection of primary human monocytes through inhibiting cellular viral restriction factors

Background

Methamphetamine (METH), a potent addictive psychostimulant, is highly prevalent in HIV-infected individuals. Clinically, METH use is implicated in alteration of immune system and increase of HIV spread/replication. Therefore, it is of importance to examine whether METH has direct effect on HIV infection of monocytes, the major target and reservoir cells for the virus.

Results

METH-treated monocytes were more susceptible to HIV infection as evidenced by increased levels of viral proteins (p24 and Pr55Gag) and expression of viral GAG gene. In addition, using HIV Bal with luciferase reporter gene (HIV Bal-eLuc), we showed that METH-treated cells expressed higher luciferase activities than untreated monocytes. Mechanistically, METH inhibited the expression of IFN-λ1, IRF7, STAT1, and the antiviral IFN-stimulated genes (ISGs: OAS2, GBP5, ISG56, Viperin and ISG15). In addition, METH down-regulated the expression of the HIV restriction microRNAs (miR-28, miR-29a, miR-125b, miR-146a, miR-155, miR-223, and miR-382).

Conclusions

METH compromises the intracellular anti-HIV immunity and facilitates HIV replication in primary human monocytes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00703-4.

Determinants of Ligand Specificity and Functional Plasticity in Type I Interferon Signaling

The Type I Interferon family of cytokines all act through the same cell surface receptor and induce phosphorylation of the same subset of response regulators of the STAT family. Despite their shared receptor, different Type I Interferons have different functions during immune response to infection. In particular, they differ in the potency of their induced anti-viral and anti-proliferative responses in target cells. It remains not fully understood how these functional differences can arise in a ligand-specific manner both at the level of STAT phosphorylation and the downstream function. We use a minimal computational model of Type I Interferon signaling, focusing on Interferon-α and Interferon-β. We validate the model with quantitative experimental data to identify the key determinants of specificity and functional plasticity in Type I Interferon signaling. We investigate different mechanisms of signal discrimination, and how multiple system components such as binding affinity, receptor expression levels and their variability, receptor internalization, short-term negative feedback by SOCS1 protein, and differential receptor expression play together to ensure ligand specificity on the level of STAT phosphorylation. Based on these results, we propose phenomenological functional mappings from STAT activation to downstream anti-viral and anti-proliferative activity to investigate differential signal processing steps downstream of STAT phosphorylation. We find that the negative feedback by the protein USP18, which enhances differences in signaling between Interferons via ligand-dependent refractoriness, can give rise to functional plasticity in Interferon-α and Interferon-β signaling, and explore other factors that control functional plasticity. Beyond Type I Interferon signaling, our results have a broad applicability to questions of signaling specificity and functional plasticity in signaling systems with multiple ligands acting through a bottleneck of a small number of shared receptors.

Targeting Inflammatory Mediators: An Anticancer Mechanism of Thymoquinone Action

BACKGROUND

Thymoquinone is a promising anticancer molecule, the chemopreventive role of which is well-known at least in vitro and in the animal model. In this review article, we focused on the anti-inflammatory activities of thymoquinone in cancer cells.

METHOD

Research data on inflammation, cancer and thymoquinone were acquired from PubMed, Scopus, Web of Science and Google Scholar. We reviewed papers published since the mid of the last century, and the most cited papers of the last ten years.

RESULTS

Studies indicate that thymoquinone possesses immunomodulatory activities, in addition to its chemopreventive role, as thymoquinone can target and modulate inflammatory molecules, like nuclear factor kappa B (NF-κβ), interleukins, tumor necrosis factor-α (TNF-α), and certain growth factors. As chronic inflammation plays an important role in cancer development, controlling inflammatory pathways is an important mechanism of an anticancer molecule, and modulation of inflammatory pathways might be one of the key mechanisms of thymoquinone's anticancer activities.

CONCLUSION

This article reviewed the role of inflammation on cancer development, and the action of thymoquinone on inflammatory molecules, which have been proved in vitro and in vivo. Much attention is required for studying the role of thymoquinone in immunotherapeutics and developing this molecule as a future anticancer drug.

Structural basis for STAT2 suppression by flavivirus NS5

Suppressing cellular signal transducers of transcription 2 (STAT2) is a common strategy viruses use to establish infections, yet the detailed mechanism remains elusive due to lack of structural information of the viral-cellular complex involved. Here, we report the cryo-EM and crystal structures of human STAT2 (hSTAT2) in complex with the non-structural protein 5 (NS5) of Zika virus (ZIKV) and dengue virus (DENV), revealing two-pronged interactions between NS5 and hSTAT2. First, the NS5 methyltransferase and RNA-dependent RNA polymerase (RdRP) domains form a conserved inter-domain cleft harboring the coiled-coil domain of hSTAT2, thus preventing association of hSTAT2 with interferon regulatory factor 9. Second, the NS5 RdRP domain also binds the N-terminal domain of hSTAT2. Disruption of these ZIKV NS5–hSTAT2 interactions compromised NS5-mediated hSTAT2 degradation and interferon suppression, and viral infection under interferon-competent condition. Taken together, these results clarify the mechanism underlying the functional antagonism of STAT2 by both ZIKV and DENV.

IFI35 as a biomolecular marker of neuroinflammation and treatment response in multiple sclerosis

Multiple Sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) with unpredictable clinical outcome. As such, there is an urgent need to identify biomarkers that can predict the treatment response. Therefore, in an open-label, clinical, paraclinical and molecular prospective study, we assessed 50 interferon (IFN) treated MS patients for Rio Score (RS)/Modified Rio Score (MRS) and densitometric expression of the interferon-induced protein 35 (IFI35), a signal-protein with potential to be clinically relevant in the management of the disease. We found 4.92-fold upregulated IFI35 in IFN-treated MS group respect to healthy controls (p < .0001) and 2.31-fold respect to untreated MS group (p < .0001). Moreover, IFI35 expression profile correlated with RS and MRS rank values (r = -0.6018, p < .0001; r = -0.620, p < .0001), white matter volume (r = -0.5041; p = .0017) and cerebral lesion load (r = -0.5075; p = .0026). Finally, the main proportion of IFN-treated MS patients non-reaching the 65% threshold in IFI35 expression leaved the RS/MRS rank value 0 in a period ranging from 5 to 15 months (p < .0001) from the study entry; instead, all patients that reaching this threshold maintained the RS/MRS value 0 until the study end (p < .0001). In conclusion, the expression level of IFI35 in untreated MS patients highlights a correlation with neuroinflammation. Furthermore, IFI35 expression in IFN-treated MS patients shows a modular correlation between dosing regimes, which is predictive for long-term clinical outcome and drug efficacy.

Thymoquinone Effects on Cell Viability, Apoptosis and VEGF-A Gene Expression Level in AGS(CRL-1739) Cell Line

BACKGROUND

Cancer is one of the most fatal diseases across the world and it was reported that 90% of cancer fatality depends on its angiogenesis potential. Black seed or Nigella sativa L. is a medicinal plant native to southwest Asia. N. sativa has been used for medicinal purposes for centuries and predominantly has bioactive components like Thymoquinone, which is used as a candidate for anti-cancer and anti-angiogenesis drugs.

METHODS

Callus was induced from leaf tissue, after that alcoholic extracts were prepared from three-month-old calluses. Thymoquinone content was measured by HPLC methods. AGS cell line was cultured and treated with standard Thymoquinone and extracts from callus. Then, cell proliferation, expression of angiogenic factor (VEGF-A gene), and apoptosis test were done by MTT assay, real-time PCR and Annexin-v kit, respectively.

RESULTS

HPLC found the maximum amount of Thymoquinone in the extract of leaf calluses, which were grown in the dark. MTT assay revealed that particular doses of extracts reduced cell proliferation. Real-time and Fluorescence- Activated Cell Sorting (FACS) results demonstrated that standard Thymoquinone and callus extracts down-regulated the VEGF-A gene expression, and all three induced apoptosis in the AGS cell line.

CONCLUSION

It has been shown that TQ has pro-apoptotic and anti-metastatic effects on stomach cancer cell line, and these properties can introduce it as an anti-cancer drug in the near future.

Transcriptional insights into the CD8+ T cell response in mono-HIV and HCV infection

Background

Disease progression in the absence of therapy varies significantly in mono-HIV and HCV infected individuals. Virus-specific CD8⁺ T cells play an important role in restricting lentiviral replication and determining the rate of disease progression during HIV and HCV mono- and co-infection. Thus, understanding the similarities in the characteristics of CD8⁺ T cells in mono-HIV and HCV infection at the transcriptomic level contributes to the development of antiviral therapy. In this study, a meta-analysis of CD8⁺ T cell gene expression profiles derived from mono-HIV and HCV infected individuals at different stages of disease progression, was conducted to understand the common changes experienced by CD8⁺ T cells.

Methods

Five microarray datasets, reporting CD8⁺ T cell mRNA expression of the mono-HIV and HCV infected patients, were retrieved from Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were identified via integrative meta-analysis of expression data (INMEX) program. Network analysis methods were used to assess protein–protein interaction (PPI) networks, Gene Ontology (GO) terms and pathway enrichment for DEGs. MirDIP and miRDB online prediction tools were used to predict potential microRNAs (miRNAs) targeting hub genes.

Results

First, we identified 625 and 154 DEGs in the CD8⁺ T cells originating from mono-HIV and HCV chronic progressor patients, respectively, compared to healthy individuals. Among them, interferon-stimulated genes (ISGs) including ISG15, IFIT3, ILI44L, CXCL8, FPR1 and TLR2, were upregulated after mono-HIV and HCV infection. Pathway enrichment analysis of DEGs showed that the “cytokine–cytokine receptor interaction” and “NF-kappa B” signaling pathways were upregulated after mono-HIV and HCV infection. In addition, we identified 92 and 50 DEGs in the CD8⁺ T cells of HIV non-progressor and HCV resolver patients, respectively, compared with corresponding chronic progressors. We observed attenuated mitosis and reduced ISG expression in HIV non-progressors and HCV resolvers compared with the corresponding chronic progressors. Finally, we identified miRNA-143-3p, predicted to target both IFIT3 in HIV and STAT5A in HCV infection.

Conclusions

We identified DEGs and transcriptional patterns in mono-HIV and HCV infected individuals at different stages of disease progression and identified miRNA-143-3p with potential to intervene disease progression, which provides a new strategy for developing targeted therapies.

Nonstructural Protein 11 of Porcine Reproductive and Respiratory Syndrome Virus Induces STAT2 Degradation To Inhibit Interferon Signaling

Interferons (IFNs) play a crucial role in host antiviral response by activating the JAK/STAT (Janus kinase/signal transducer and activator of transcription) signaling pathway to induce the expression of myriad genes. STAT2 is a key player in the IFN-activated JAK/STAT signaling. Porcine reproductive and respiratory syndrome virus (PRRSV) is an important viral pathogen, causing huge losses to the swine industry. PRRSV infection elicits a meager protective immune response in pigs. The objective of this study was to investigate the effect of PRRSV on STAT2 signaling. Here, we demonstrated that PRRSV downregulated STAT2 to inhibit IFN-activated signaling. PRRSV strains of both PRRSV-1 and PRRSV-2 species reduced the STAT2 protein level, whereas the STAT2 transcript level had minimal change. PRRSV reduced the STAT2 level in a dose-dependent manner and shortened STAT2 half-life significantly from approximately 30 to 5 h. PRRSV-induced STAT2 degradation could be restored by treatment with the proteasome inhibitor MG132 and lactacystin. In addition, PRRSV nonstructural protein 11 (nsp11) was identified to interact with and reduce STAT2. The N-terminal domain (NTD) of nsp11 was responsible for STAT2 degradation and interacted with STAT2 NTD and the coiled-coil domain. Mutagenesis analysis showed that the amino acid residue K59 of nsp11 was indispensable for inducing STAT2 reduction. Mutant PRRSV with the K59A mutation generated by reverse genetics almost lost the ability to reduce STAT2. Together, these results demonstrate that PRRSV nsp11 antagonizes IFN signaling via mediating STAT2 degradation and provide further insights into the PRRSV interference of the innate immunity.IMPORTANCE PRRSV infection elicits a meager protective immune response in pigs. One of the possible reasons is that PRRSV antagonizes interferon induction and its downstream signaling. Interferons are key components in the innate immunity and play crucial roles against viral infection and in the activation of adaptive immune response via JAK/STAT signaling. STAT2 is indispensable in the JAK/STAT signaling since it is also involved in activation of antiviral activity in the absence of STAT1. Here, we discovered that PRRSV nsp11 downregulates STAT2. Interestingly, the N-terminal domain of nsp11 is responsible for inducing STAT2 degradation and directly interacts with STAT2 N-terminal domain. We also identified a crucial amino acid residue K59 in nsp11 since a mutation of it led to loss of the ability to downregulate STAT2. A mutant PRRSV with mutation of K59 had minimal effect on STAT2 reduction. Our data provide further insights into PRRSV interference with interferon signaling.

Transcriptome profiles in sarcoidosis and their potential role in disease prediction

PURPOSE OF REVIEW

Sarcoidosis is a systemic disease defined by the presence of nonnecrotizing granuloma in the absence of any known cause. Although the heterogeneity of sarcoidosis is well characterized clinically, the transcriptome of sarcoidosis and underlying molecular mechanisms are not. The signal of all transcripts, small and long noncoding RNAs, can be detected using microarrays or RNA-Sequencing. Analyzing the transcriptome of tissues that are directly affected by granulomas is of great importance to understand biology of the disease and may be predictive of disease and treatment outcome.

RECENT FINDINGS

Multiple genome wide expression studies performed on sarcoidosis affected tissues were published in the last 11 years. Published studies focused on differences in gene expression between sarcoidosis vs. control tissues, stable vs. progressive sarcoidosis, as well as sarcoidosis vs. other diseases. Strikingly, all these transcriptomics data confirm the key role of TH1 immune response in sarcoidosis and particularly of interferon-γ (IFN-γ) and type I IFN-driven signaling pathways.

SUMMARY

The steps toward transcriptomics of sarcoidosis in precision medicine highlight the potentials of this approach. Large prospective follow-up studies are required to identify signatures predictive of disease progression and outcome.

Human Cytomegalovirus Utilizes a Nontraditional Signal Transducer and Activator of Transcription 1 Activation Cascade via Signaling through Epidermal Growth Factor Receptor and Integrins To Efficiently Promote the Motility, Differentiation, and Polarization of Infected Monocytes

Human cytomegalovirus (HCMV) infects peripheral blood monocytes and triggers biological changes that promote viral dissemination and persistence. We have shown that HCMV induces a proinflammatory state in infected monocytes, resulting in enhanced monocyte motility and transendothelial migration, prolonged monocyte survival, and differentiation toward a long-lived M1-like macrophage phenotype. Our data indicate that HCMV triggers these changes, in the absence of de novo viral gene expression and replication, through engagement and activation of epidermal growth factor receptor (EGFR) and integrins on the surface of monocytes. We previously identified that HCMV induces the upregulation of multiple proinflammatory gene ontologies, with the interferon-associated gene ontology exhibiting the highest percentage of upregulated genes. However, the function of the HCMV-induced interferon (IFN)-stimulated genes (ISGs) in infected monocytes remained unclear. We now show that HCMV induces the enhanced expression and activation of a key ISG transcriptional regulator, signal transducer and activator of transcription (STAT1), via an IFN-independent but EGFR- and integrin-dependent signaling pathway. Furthermore, we identified a biphasic activation of STAT1 that likely promotes two distinct phases of STAT1-mediated transcriptional activity. Moreover, our data show that STAT1 is required for efficient early HCMV-induced enhanced monocyte motility and later for HCMV-induced monocyte-to-macrophage differentiation and for the regulation of macrophage polarization, suggesting that STAT1 may serve as a molecular convergence point linking the biological changes that occur at early and later times postinfection. Taken together, our results suggest that HCMV reroutes the biphasic activation of a traditionally antiviral gene product through an EGFR- and integrin-dependent pathway in order to help promote the proviral activation and polarization of infected monocytes.IMPORTANCE HCMV promotes multiple functional changes in infected monocytes that are required for viral spread and persistence, including their enhanced motility and differentiation/polarization toward a proinflammatory M1 macrophage. We now show that HCMV utilizes the traditionally IFN-associated gene product, STAT1, to promote these changes. Our data suggest that HCMV utilizes EGFR- and integrin-dependent (but IFN-independent) signaling pathways to induce STAT1 activation, which may allow the virus to specifically dictate the biological activity of STAT1 during infection. Our data indicate that HCMV utilizes two phases of STAT1 activation, which we argue molecularly links the biological changes that occur following initial binding to those that continue to occur days to weeks following infection. Furthermore, our findings may highlight a unique mechanism for how HCMV avoids the antiviral response during infection by hijacking the function of a critical component of the IFN response pathway.

Native Hydrophobic Binding Interactions at the Transition State for Association between the TAZ1 Domain of CBP and the Disordered TAD-STAT2 Are Not a Requirement

A significant fraction of the eukaryotic proteome consists of proteins that are either partially or completely disordered under native-like conditions. Intrinsically disordered proteins (IDPs) are common in protein-protein interactions and are involved in numerous cellular processes. Although many proteins have been identified as disordered, much less is known about the binding mechanisms of the coupled binding and folding reactions involving IDPs. Here we have analyzed the rate-limiting transition state for binding between the TAZ1 domain of CREB binding protein and the intrinsically disordered transactivation domain of STAT2 (TAD-STAT2) by site-directed mutagenesis and kinetic experiments (Φ-value analysis) and found that the native protein-protein binding interface is not formed at the transition state for binding. Instead, native hydrophobic binding interactions form late, after the rate-limiting barrier has been crossed. The association rate constant in the absence of electrostatic enhancement was determined to be rather high. This is consistent with the Φ-value analysis, which showed that there are few or no obligatory native contacts. Also, linear free energy relationships clearly demonstrate that native interactions are cooperatively formed, a scenario that has usually been observed for proteins that fold according to the so-called nucleation-condensation mechanism. Thus, native hydrophobic binding interactions at the rate-limiting transition state for association between TAD-STAT2 and TAZ1 are not a requirement, which is generally in agreement with previous findings on other IDP systems and might be a common mechanism for IDPs.

Medical comorbidity in bipolar disorder: The link with metabolic-inflammatory systems

BACKGROUND

Bipolar disorder (BD) is associated with chronic low-grade inflammation, several medical comorbidities and a decreased life expectancy. Metabolic-inflammatory changes have been postulated as one of the main links between BD and medical comorbidity, although there are few studies exploring possible mechanisms underlying this relationship. Therefore, the aims of the current narrative review were 1) synthesize the evidence for metabolic-inflammatory changes that may facilitate the link between medical comorbidity and BD and 2) discuss therapeutic and preventive implications of these pathways.

METHODS

The PubMed and Google Scholar databases were searched for relevant studies.

RESULTS

Identified studies suggested that there is an increased risk of medical comorbidities, such as autoimmune disorders, obesity, diabetes and cardiovascular disease in patients with BD. The association between BD and general medical comorbidities seems to be bidirectional and potentially mediated by immune dysfunction. Targeting the metabolic-inflammatory-mood pathway may potential yield improved outcomes in BD; however, further study is needed to determine which specific interventions may be beneficial.

LIMITATIONS

The majority of identified studies had cross-sectional designs, small sample sizes and limited measurements of inflammation.

CONCLUSIONS

Treatment and prevention of general medical comorbidities in mood disorders should include preferential prescribing of metabolically neutral agents and adjunctive lifestyle modifications including increased physical activity, improved diet and decreased substance abuse. In addition, the use of anti-inflammatory agents could be a relevant therapeutic target in future research.

Type I Interferons Modulate CD8+ T Cell Immunity to mRNA Vaccines

mRNA vaccines have emerged as potent tools to elicit antitumor T cell immunity. They are characterized by a strong induction of type I interferons (IFNs), potent inflammatory cytokines affecting T cell differentiation and survival. Recent reports have attributed opposing roles for type I IFNs in modulating CD8+ T cell immunity to mRNA vaccines, from profoundly stimulatory to strongly inhibitory. The mechanisms behind this duality are unclear. Disentangling the factors governing the beneficial or detrimental impact of type I IFNs on CD8+ T cell responses is vital to the design of mRNA vaccines of increased potency. In light of recent advancements regarding the complex role of type I IFNs in regulating CD8+ T cell immunity to infectious diseases, we posit that the dual outcome of type I IFNs on CD8+ T cell responses to mRNA vaccination is determined by the timing and intensity of type I IFN induction relative to T cell receptor (TCR) activation.

Interferon (IFN)-induced protein 35 (IFI35) negatively regulates IFN-β-phosphorylated STAT1-RIG-I-CXCL10/CCL5 axis in U373MG astrocytoma cells treated with polyinosinic-polycytidylic acid

Interferon (IFN)-stimulated genes (ISGs) exert multiple functions in immune system. IFN-induced protein 35 (IFI35) is a member of ISGs, and has been suggested to regulate innate immune reaction. However, the physiological functions and pathological roles of IFI35 in the central nervous system are not characterized well. In the present study, we found that the expression of IFI35 was induced by a Toll-like receptor 3 (TLR3) ligand polyinosinic-polycytidylic acid (poly IC) in U373MG human astrocytoma cells. Knockdown of IFI35 using RNA interference resulted in increased expression of IFN-β, phosphorylated STAT1 (P-STAT1), retinoic acid-inducible gene-I (RIG-I), CXCL10 and CCL5 induced by poly IC. Poly IC-induced expression of CXCL10 and CCL5 was decreased by knockdown of RIG-I. These results suggest that IFI35 may negatively regulate the TLR3-IFN-β-P-STAT1-RIG-I-CXCL10/CCL5 axis in U373MG cells, and IFI35 may play a role at least partially in the regulation of innate immune reactions in astrocytes.

Non-Canonical Role of IKKα in the Regulation of STAT1 Phosphorylation in Antiviral Signaling

Non-self RNA is recognized by retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), inducing type I interferons (IFNs). Type I IFN promotes the expression of IFN-stimulated genes (ISGs), which requires the activation of signal transducer and activator of transcription-1 (STAT1). We previously reported that dsRNA induced STAT1 phosphorylation via a type I IFN-independent pathway in addition to the well-known type I IFN-dependent pathway. IκB kinase α (IKKα) is involved in antiviral signaling induced by dsRNA; however, its role is incompletely understood. Here, we explored the function of IKKα in RLR-mediated STAT1 phosphorylation. Silencing of IKKα markedly decreased the level of IFN-β and STAT1 phosphorylation inHeH response to dsRNA. However, the inhibition of IKKα did not alter the RLR signaling-mediated dimerization of interferon responsive factor 3 (IRF3) or the nuclear translocation of nuclear factor-κB (NFκB). These results suggest a non-canonical role of IKKα in RLR signaling. Furthermore, phosphorylation of STAT1 was suppressed by IKKα knockdown in cells treated with a specific neutralizing antibody for the type I IFN receptor (IFNAR) and in IFNAR-deficient cells. Collectively, the dual regulation of STAT1 by IKKα in antiviral signaling suggests a role for IKKα in the fine-tuning of antiviral signaling in response to non-self RNA.

Receptor dimer stabilization by hierarchical plasma membrane microcompartments regulates cytokine signaling

The interaction dynamics of signaling complexes is emerging as a key determinant that regulates the specificity of cellular responses. We present a combined experimental and computational study that quantifies the consequences of plasma membrane microcompartmentalization for the dynamics of type I interferon receptor complexes. By using long-term dual-color quantum dot (QD) tracking, we found that the lifetime of individual ligand-induced receptor heterodimers depends on the integrity of the membrane skeleton (MSK), which also proved important for efficient downstream signaling. By pair correlation tracking and localization microscopy as well as by fast QD tracking, we identified a secondary confinement within ~300-nm-sized zones. A quantitative spatial stochastic diffusion-reaction model, entirely parameterized on the basis of experimental data, predicts that transient receptor confinement by the MSK meshwork allows for rapid reassociation of dissociated receptor dimers. Moreover, the experimentally observed apparent stabilization of receptor dimers in the plasma membrane was reproduced by simulations of a refined, hierarchical compartment model. Our simulations further revealed that the two-dimensional association rate constant is a key parameter for controlling the extent of MSK-mediated stabilization of protein complexes, thus ensuring the specificity of this effect. Together, experimental evidence and simulations support the hypothesis that passive receptor confinement by MSK-based microcompartmentalization promotes maintenance of signaling complexes in the plasma membrane.

Genome-Wide STAT3 Binding Analysis after Histone Deacetylase Inhibition Reveals Novel Target Genes in Dendritic Cells

STAT3 is a master transcriptional regulator that plays an important role in the induction of both immune activation and immune tolerance in dendritic cells (DCs). The transcriptional targets of STAT3 in promoting DC activation are becoming increasingly understood; however, the mechanisms underpinning its role in causing DC suppression remain largely unknown. To determine the functional gene targets of STAT3, we compared the genome-wide binding of STAT3 using ChIP sequencing coupled with gene expression microarrays to determine STAT3-dependent gene regulation in DCs after histone deacetylase (HDAC) inhibition. HDAC inhibition boosted the ability of STAT3 to bind to distinct DNA targets and regulate gene expression. Among the top 500 STAT3 binding sites, the frequency of canonical motifs was significantly higher than that of noncanonical motifs. Functional analysis revealed that after treatment with an HDAC inhibitor, the upregulated STAT3 target genes were those that were primarily the negative regulators of proinflammatory cytokines and those in the IL-10 signaling pathway. The downregulated STAT3-dependent targets were those involved in immune effector processes and antigen processing/presentation. The expression and functional relevance of these genes were validated. Specifically, functional studies confirmed that the upregulation of IL-10Ra by STAT3 contributed to the suppressive function of DCs following HDAC inhibition.

Artesunate inhibits type I interferon-induced production of macrophage migration inhibitory factor in patients with systemic lupus erythematosus

OBJECTIVE

Macrophage migration inhibitory factor (MIF) is a key regulator of both atherosclerosis and systemic lupus erythematosus (SLE), yet factors leading to its overproduction remain unclear. To explore regulation of MIF in SLE, we studied effects and potential mechanisms of type I interferon (IFN) and artesunate (ART), an antimalarial agent extracted from Chinese herbs, on levels of MIF.

METHODS

Serum and peripheral blood cells from SLE patients and healthy controls were measured for MIF levels by ELISA and type I IFN-inducible gene expressions by real-time PCR, respectively, and assessed for associations by Spearman correlation. ART was added to human umbilical vein endothelial cell (HUVEC) cultures with or without prior IFNα-1b stimulation and to SLE peripheral blood mononuclear cell (PBMC) cultures. Protein levels of STATs and phosphorylated (p-) STATs in HUVECs were determined by Western blotting.

RESULTS

Serum MIF levels were elevated in SLE patients and positively associated with disease activity (r = 0.86, p < 0.0001), accumulated damage (r = 0.34, p < 0.05), and IFN scores in SLE PBMCs (r = 0.74, p = 0.0002). The addition of IFNα-1b promoted MIF production in a time- and dose-dependent manner in HUVEC cultures. ART could inhibit expressions of IFN-inducible genes (LY6E and ISG15) in both HUVEC and SLE PBMC cultures, and suppress MIF production and over-expression of p-STAT1, but not p-STAT3 or STAT5, induced by IFNα-1b stimulation. IFNγ-induced expression of p-STAT1 in HUVECs was not inhibited by ART.

CONCLUSION

MIF could be regulated by type I IFN in SLE patients. ART counteracts the effect of IFNα to inhibit MIF production by blocking STAT1 phosphorylation and thus may have therapeutic potential for SLE-associated atherosclerosis.

STAT3 regulates hypoxia-induced epithelial mesenchymal transition in oesophageal squamous cell cancer

Hypoxia plays a key role in tumour initiation and metastasis; one of the mechanisms is to induce epithelial-mesenchymal transition (EMT). Signal transducer and activator of transcription 3 (STAT3) is involved in EMT by regulating the transcriptional regulators of E-cadherin, the biomarker of EMT. Until now, however, few studies have focused on the effects of STAT3 in hypoxia-induced EMT in tumour cells. The goal of this study was to investigate the roles of STAT3 in hypoxia-induced EMT in oesophageal squamous cell carcinoma (ESCC). The ESCC cells, TE-1 and EC-1, were incubated in normoxia, or in CoCl₂, which was used to mimic hypoxia. With CoCl₂, the ESCC cells showed increased migration and invasion abilities, accompanied with upregulation of HIF-1α, STAT3, and vimentin, and downregulation of E-cadherin. Knockdown of STAT3 inhibited EMT of ESCC cells and downregulated HIF-1α in vitro and in vivo. In ChIP assays, STAT3 bound to the promoter of HIF-1α, suggesting that STAT3 regulates transcription of HIF-1α. In conclusion, hypoxia induces EMT of ESCC, and STAT3 regulates this process by promoting HIF-1α expression.

Beryllium-induced lung disease exhibits expression profiles similar to sarcoidosis

A subset of beryllium-exposed workers develop beryllium sensitisation (BeS) which precedes chronic beryllium disease (CBD). We conducted an in-depth analysis of differentially expressed candidate genes in CBD.We performed Affymetrix GeneChip 1.0 ST array analysis on peripheral blood mononuclear cells (PBMCs) from 10 CBD, 10 BeS and 10 beryllium-exposed, nondiseased controls stimulated with BeSO4 or medium. The differentially expressed genes were validated by high-throughput real-time PCR in this group and in an additional group of cases and nonexposed controls. The functional roles of the top candidate genes in CBD were assessed using a pharmacological inhibitor. CBD gene expression data were compared with whole blood and lung tissue in sarcoidosis from the Gene Expression Omnibus.We confirmed almost 450 genes that were significantly differentially expressed between CBD and controls. The top enrichment of genes was for JAK (Janus kinase)-STAT (signal transducer and activator of transcription) signalling. A JAK2 inhibitor significantly decreased tumour necrosis factor-α and interferon-γ production. Furthermore, we found 287 differentially expressed genes overlapped in CBD/sarcoidosis. The top shared pathways included cytokine-cytokine receptor interactions, and Toll-like receptor, chemokine and JAK-STAT signalling pathways.We show that PBMCs demonstrate differentially expressed gene profiles relevant to the immunnopathogenesis of CBD. CBD and sarcoidosis share similar differential expression of pathogenic genes and pathways.

Blockage of STAT3 Signaling Pathway by Morusin Induces Apoptosis and Inhibits Invasion in Human Pancreatic Tumor Cells

OBJECTIVES

Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor implicated in carcinogenesis. Here, we investigated the role of morusin, the major prenylflavonoid, isolated from Chinese herbal medicine in abrogating the constitutive STAT3 activation in human pancreatic tumor cells.

METHODS

The effect of morusin on STAT3 activation, associated protein kinases, STAT3-regulated gene products, cellular proliferation, and apoptosis was examined.

RESULTS

Morusin specifically inhibited constitutive STAT3 activation both at tyrosine residue 705 and serine residue 727 in 4 pancreatic tumor cells. The inhibition of STAT3 was mediated through the suppression of activation of upstream JAK1, JAK2, and c-Src kinases. Morusin led to the accumulation of the cells in different phases of the cell cycle and caused induction of apoptosis and loss of mitochondrial membrane potential. Morusin downregulated the expression of various STAT3-regulated gene products; this correlated with induction of caspase-3 activation and anti-invasive effects. Treatment with the protein tyrosine phosphatase inhibitor pervanadate reversed the morusin-induced downregulation of STAT3, thereby suggesting the involvement of a protein tyrosine phosphatase.

CONCLUSIONS

Morusin is a novel blocker of STAT3 activation and thus may have potential in negative regulation of growth and metastasis of pancreatic tumor cells.

Brassinin inhibits STAT3 signaling pathway through modulation of PIAS-3 and SOCS-3 expression and sensitizes human lung cancer xenograft in nude mice to paclitaxel

Persistent phosphorylation of signal transducers and activators of transcription 3 (STAT3) is frequently observed in tumor cells. We found that brassinin (BSN) suppressed both constitutive and IL-6-inducible STAT3 activation in lung cancer cells. Moreover, BSN induced PIAS-3 protein and mRNA, whereas the expression of SOCS-3 was reduced. Knockdown of PIAS-3 by small interfering RNA prevented inhibition of STAT3 and cytotoxicity by BSN. Overexpression of SOCS-3 in BSN-treated cells increased STAT3 phosphorylation and cell viability. BSN down-regulated STAT3-regulated gene products, inhibited proliferation, invasion, as well as induced apoptosis. Most importantly, when administered intraperitoneally, combination of BSN and paclitaxel significantly decreased the tumor development in a xenograft lung cancer mouse model associated with down-modulation of phospho-STAT3, Ki-67 and CD31. We suggest that BSN inhibits STAT3 signaling through modulation of PIAS-3 and SOCS-3, thereby attenuating tumor growth and increasing sensitivity to paclitaxel.

Characterization of a Novel Human-Specific STING Agonist that Elicits Antiviral Activity Against Emerging Alphaviruses

Pharmacologic stimulation of innate immune processes represents an attractive strategy to achieve multiple therapeutic outcomes including inhibition of virus replication, boosting antitumor immunity, and enhancing vaccine immunogenicity. In light of this we sought to identify small molecules capable of activating the type I interferon (IFN) response by way of the transcription factor IFN regulatory factor 3 (IRF3). A high throughput in vitro screen yielded 4-(2-chloro-6-fluorobenzyl)-N-(furan-2-ylmethyl)-3-oxo-3,4-dihydro-2H-benzo[b][1,4]thiazine-6-carboxamide (referred to herein as G10), which was found to trigger IRF3/IFN-associated transcription in human fibroblasts. Further examination of the cellular response to this molecule revealed expression of multiple IRF3-dependent antiviral effector genes as well as type I and III IFN subtypes. This led to the establishment of a cellular state that prevented replication of emerging Alphavirus species including Chikungunya virus, Venezuelan Equine Encephalitis virus, and Sindbis virus. To define cellular proteins essential to elicitation of the antiviral activity by the compound we employed a reverse genetics approach that utilized genome editing via CRISPR/Cas9 technology. This allowed the identification of IRF3, the IRF3-activating adaptor molecule STING, and the IFN-associated transcription factor STAT1 as required for observed gene induction and antiviral effects. Biochemical analysis indicates that G10 does not bind to STING directly, however. Thus the compound may represent the first synthetic small molecule characterized as an indirect activator of human STING-dependent phenotypes. In vivo stimulation of STING-dependent activity by an unrelated small molecule in a mouse model of Chikungunya virus infection blocked viremia demonstrating that pharmacologic activation of this signaling pathway may represent a feasible strategy for combating emerging Alphaviruses.

Spatiotemporally Controlled Reorganization of Signaling Complexes in the Plasma Membrane of Living Cells

Triggered immobilization of proteins in the plasma membrane of living cells into functional micropatterns is established by using an adaptor protein, which is comprised of an antiGFP nanobody fused to the HaloTag protein. Efficient in situ reorganization of the type I interferon receptor subunits as well as intact, fully functional signaling complexes in living cells are achieved by this method.

GSK3β inhibition protects the immature brain from hypoxic-ischaemic insult via reduced STAT3 signalling

Hypoxic-ischaemic (HI) injury is an important cause of neurological morbidity in neonates. HI leads to pathophysiological responses, including inflammation and oxidative stress that culminate in cell death. Activation of glycogen synthase kinase 3β (GSK3β) and the signal transducer and activator of transcription (STAT3) promotes brain inflammation. The purpose of this study was to test whether inhibition of GSK3β signalling protects against neonatal HI brain injury. Mice were subjected to HI at postnatal day (PND) 9 and treated with a selective GSK3β inhibitor, SB216763. Brain injury and caspase-3 activation, anti-oxidant and inflammatory mRNA responses and activation of STAT3 were analysed. Our results show that HI reduced phosphorylation of GSK3β, thus promoting its kinase activity. The GSK3β inhibitor reduced caspase-3 activation and neuronal cell death elicited by HI and reverted the effects of HI on gene expression of the anti-oxidant enzyme sod2 and mitochondrial factor pgc1α. The HI insult activated STAT3 in glial cells and GSK3β inhibition attenuated STAT3 phosphorylation and its nuclear translocation following HI. Further, GSK3β inhibition reduced HI-induced gene expression of pro-inflammatory cytokines tnfα and Il-6, while promoted the anti-inflammatory factor Il-10. In summary, data show that GSK3β inhibition is neuroprotective in neonatal HI brain injury likely via reduced pro-inflammatory responses by blocking STAT3 signalling. Our study suggests that pharmacological interventions built upon GSK3β silencing strategies could represent a novel therapy in neonatal brain injury.

Carnosic acid inhibits STAT3 signaling and induces apoptosis through generation of ROS in human colon cancer HCT116 cells

Carnosic acid (CA), the main antioxidant compound of Rosmarinus officinalis L., has been reported to possess anticancer activity. However, the molecular mechanisms underlying the anticancer effects of CA remain poorly understood. Our study revealed that CA treatment significantly reduced the viability of human colon cancer HCT116, SW480, and HT-29 cells. Treatment with CA induced apoptosis, which was associated with the induction of p53 and Bax, inhibition of Mdm2, Bcl-2, and Bcl-xl expression, activation of caspase-9, and -3, and the cleavage of PARP in HCT116 cells. CA inhibited the constitutive phosphorylation, the DNA binding and the reporter gene activity of STAT3 in HCT116 cells by blocking the phosphorylation of upstream JAK2 and Src kinases. Moreover, CA attenuated the expression of STAT3 target gene products, such as survivin, cyclin D1, D2, and D3. In STAT3-overexpressed HCT116 cells, CA inhibited cell viability and the expression of cyclin D1 and survivin. Furthermore, CA treatment induced the generation of ROS in these colon cancer cells. Pretreatment of cells with ROS scavenger N-acetyl cysteine abrogated the inhibitory effect of CA on the JAK2-STAT3/Src-STAT3 signaling and rescued cells from CA-induced apoptosis by blocking the induction of p53 and the cleavage of caspase-3 and PARP in HCT116 cells. However, L-buthionine-sulfoximine, a pharmacological inhibitor of GSH synthesis, increased CA-induced ROS production, thereby potentiating apoptotic effect of CA. In conclusion, our study provides the first report that CA induced apoptosis in HCT116 cells via generation of ROS, induction of p53, activation of caspases, and inhibition of STAT3 signaling pathway. © 2015 Wiley Periodicals, Inc.

Enrichment pathway analysis. The inflammatory genetic background in Bipolar Disorder

INTRODUCTION

The pathophysiology of Bipolar Disorder (BD) is yet to be fully characterized. In the last years attention was focused on neurodevelopment or neurodegenerative events. In this context, hyper- and hypo- activation of inflammatory cascades may play a role in modulating the architecture and function of neuronal tissues. In the present paper we tested the enrichment of molecular pathways related to inflammatory cascades (IL-1, IL-2, IL-6, IL-8, TNF and INF) testing whether genes related to these systems hold more variations associated with the risk for BD than expected.

METHODS

~7000 bipolar patients and controls with genome-wide data available from NIMH dataset were analyzed. SNPs were imputed, checked for quality control, pruned and tested for association (0.01<p). Fisher test was conducted to test the enrichment within the pathways and the association was permutated (10(5) times) to limit false positive findings.

RESULTS

As a result, IL-6, IL-8 and IFN related pathways held twice to thrice the number of expected variants associated with BD. These tests resisted the permutation analysis.

LIMITATIONS

The restricted number of inflammatory components included in the analysis and the lack of functional consequences for some of the SNPs analyzed may be biased; however, these choices helped the authors to lighten the statistical computational load for the analyses and at the same time included possibly hidden SNPs in linkage disequilibrium with the analyzed variations.

CONCLUSIONS

We bring evidence that the inflammatory cascades may be genetically varied in Bipolar patients. This genetic background may explain part of the pathophysiology of the disorder.

Matrine suppresses cell growth of human chronic myeloid leukemia cells via its inhibition of the interleukin-6/Janus activated kinase/signal transducer and activator of transcription 3 signaling cohort

Matrine, alkaloid isolated from Sophora flavescens, is known to be pleiotropic by exerting anti-inflammatory, anti-oxidation, as well as anti-cancer effects. However, the precise molecular targets or pathways responsible for its activities still remain unclear. The present study aimed to determine the underlying mechanisms of matrine in inhibiting the chronic myeloid leukemia cells (CML). It was observed that matrine treatment significantly suppressed CML cells proliferation, induced apoptosis and resulted in the accumulation of cells in the G0/G1 phase, accompanied by a significant decrease in Bcl-xL, Cyclin D1, and c-Myc expression. Western blot analyses revealed that matrine treatment resulted in the down-regulation in phospho-STAT3 and phospho-JAK2 without significantly effects on STAT3 and JAK2 protein levels. Matrine significantly reduced the expression of IL-6, a potent upstream activating factor of STAT3. These results strongly suggested the IL-6/JAK/STAT3 pathway play an important role in matrine's anti-leukemia effects in K562 cells.

Desferrioxamine, an iron chelator, inhibits CXCL10 expression induced by polyinosinic-polycytidylic acid in U373MG human astrocytoma cells

Although iron is essential in physiological processes, accumulation of iron in central nervous system is associated with various neurological diseases including Alzheimer's disease and Parkinson's disease. Innate immune reactions are involved in the pathogenesis of those diseases, but roles of iron in innate immunity are not known well. In the present study, pretreatment of U373MG human astrocytoma cells with an iron chelator desferrioxamine (DFX) inhibited the expression of CXCL10 induced by a Toll-like receptor 3 (TLR3) agonist polyinosinic-polycytidylic acid (poly IC). Induction of interferon-β (IFN-β) was not affected, but phosphorylation of signal transducer and transcription 1 (STAT1) was decreased by DFX. We have previously reported that various IFN-stimulated genes (ISGs) are involved in CXCL10 induction by poly IC. Pretreatment with DFX also decreased the expression of these ISGs. Pretreatment of cells with FeSO4 counteracted inhibitory effects of DFX on ISG56, retinoic acid-inducible gene-I (RIG-I), CXCL10 and phosphorylation of STAT1. These results suggest that iron may positively regulate STAT1 phosphorylation and following signaling to express ISG56, RIG-I and CXCL10 in U373MG cells treated with poly IC. Iron may contribute to innate immune and inflammatory reactions elicited by the TLR3 signaling in astrocytes, and may play an important role in neuroinflammatory diseases.

Structural and functional characterization of salmon STAT1, STAT2 and IRF9 homologs sheds light on interferon signaling in teleosts

Mammalian IRF9 and STAT2, together with STAT1, form the ISGF3 transcription factor complex, which is critical for type I interferon (IFN)-induced signaling, while IFNγ stimulation is mediated by homodimeric STAT1 protein. Teleost fish are known to possess most JAK and STAT family members, however, description of their functional activity in lower vertebrates is still scarce. In the present study we have identified two different STAT2 homologs and one IRF9 homolog from Atlantic salmon (Salmo salar). Both proteins have domain-like structures with functional motifs that are similar to higher vertebrates, suggesting that they are orthologs to mammalian STAT2 and IRF9. The two identified salmon STAT2s, named STAT2a and STAT2b, showed high sequence identity but were divergent in their transactivation domain (TAD). Like STAT1, ectopically expressed STAT2a and b were shown to be tyrosine phosphorylated by type I IFNs and, interestingly, also by IFNγ. Microscopy analyses demonstrated that STAT2 co-localized with STAT1a in the cytoplasm of unstimulated cells, while IFNa1 and IFNγ stimulation seemed to favor their nuclear localization. Overexpression of STAT2a or STAT2b together with STAT1a activated a GAS-containing reporter gene construct in IFNγ-stimulated cells. The highest induction of GAS promoter activation was found in IFNγ-stimulated cells transfected with IRF9 alone. Taken together, these data suggest that salmon STAT2 and IRF9 may have a role in IFNγ-induced signaling and promote the expression of GAS-driven genes in bony fish. Since mammalian STAT2 is primarily an ISGF3 component and not involved in IFNγ signaling, our finding features a novel role for STAT2 in fish.

STAT2: A shape-shifting anti-viral super STAT

STAT2 is unique among the STAT family of transcription factors in that its activation is driven predominantly by only two classes of cell surface receptors: Type I and III interferon receptors. As such, STAT2 plays a critical role in host defenses against viral infections. Viruses have evolved to target STAT2 by either inhibiting its expression, blocking its activity, or by targeting it for degradation. Consequently, these viral onslaughts have driven remarkable divergence in the STAT2 gene across species that is not observed in other STAT family members. Thus, the evolution of STAT2 may preserve its activity and protect each species in the face of an ever-changing viral community.

HspB1, HspB5 and HspB4 in Human Cancers: Potent Oncogenic Role of Some of Their Client Proteins

Human small heat shock proteins are molecular chaperones that regulate fundamental cellular processes in normal unstressed cells as well as in many cancer cells where they are over-expressed. These proteins are characterized by cell physiology dependent changes in their oligomerization and phosphorylation status. These structural changes allow them to interact with many different client proteins that subsequently display modified activity and/or half-life. Nowdays, the protein interactomes of small Hsps are under intense investigations and will represent, when completed, key parameters to elaborate therapeutic strategies aimed at modulating the functions of these chaperones. Here, we have analyzed the potential pro-cancerous roles of several client proteins that have been described so far to interact with HspB1 (Hsp27) and its close members HspB5 (αB-crystallin) and HspB4 (αA-crystallin).

8-hydrocalamenene, derived from Reynoutria elliptica, suppresses constitutive STAT3 activation, inhibiting proliferation and enhancing chemosensitization of human multiple myeloma cells

The identification of the active compounds of herbal medicines and the molecular targets of those compounds is an attractive therapeutic objective. Reynoutria elliptica has been used for the treatment of various inflammatory diseases as a Korean folk remedy. Based on the evidence that anti-inflammatory agents frequently exert antiproliferative activity, we tested two sesquiterpene derivatives, 8-hydrocalamenene (HC) and 8,14-dihydrocalamenene (DHC), for their ability to induce apoptosis and suppress signal transducer and activator of transcription 3 (STAT3) activation in multiple myeloma (MM) U266 cells. We found that HC inhibited cell viability in U266, but not in peripheral blood mononuclear cells. HC exerted significant cytotoxicity and induced substantial subG1-phase arrest and apoptosis as compared with DHC. HC inhibited the expression of gene products involved in antiapoptosis (Bcl-2 and Bcl-xL), proliferation (cyclin D1), and invasion (MMP-9), all of which are known to be regulated by STAT3. Furthermore, HC up-regulated cyclin-dependent kinase inhibitor p21 and induced apoptosis through the activation of caspase-8, -9, and -3 in U266 cells. Interestingly, HC blocked constitutive STAT3 activation through the inhibition of activation of upstream kinases Janus-like kinase 1 (JAK1), JAK2, and c-Src and up-regulated PIAS3. Deletion of STAT3 reversed cytotoxic effects and the down-regulation of cyclin D1 and c-myc by HC in MM cells. Finally, this sesquiterpene significantly synergized the cytotoxic and apoptotic effects of bortezomib in U266 cells. Taken together, these results suggest that HC is a novel blocker of STAT3 activation which may have a potential in the prevention and treatment of MM.

Novel antiviral host factor, TNK1, regulates IFN signaling through serine phosphorylation of STAT1

In response to viral infection, the host induces over 300 IFN-stimulated genes (ISGs), which are the central component of intracellular antiviral innate immunity. Inefficient induction of ISGs contributes to poor control and persistence of hepatitis C virus infection. Therefore, further understanding of the hepatocytic ISG regulation machinery will guide us to an improved management strategy against hepatitis C virus infection. In this study, comprehensive genome-wide, high-throughput cDNA screening for genes regulating ISG expression identified a tyrosine kinase nonreceptor 1 (TNK1) as a unique player in the ISG induction pathway. The immune-modulatory function of TNK1 has never been studied, and this study characterizes its significance in antiviral innate immunity. TNK1 is abundantly expressed in hepatocytes and maintains basal ISG expression. More importantly, TNK1 plays a critical role in type I IFN-mediated ISG induction. We discovered that the activated IFN receptor complex recruits TNK1 from the cytoplasm. TNK1 is then phosphorylated to enhance its kinase activity. The activated TNK1 potentiates JAK-STAT signaling through dual phosphorylation of STAT1 at tyrosine 701 and serine 727 amino acid positions. Our loss-of-function approach demonstrated that TNK1 governs a cluster of ISG expression that defines the TNK1 pathway effector genes. More importantly, TNK1 abundance is inversely correlated to viral replication efficiency and is also a determinant factor for the hepatocytic response to antiviral treatment. Taken together, our studies found a critical but unidentified integrated component of the IFN-JAK-STAT signaling cascade.

Targeting the STAT3 signaling pathway in cancer: role of synthetic and natural inhibitors

Signal transducers and activators of transcription (STATs) comprise a family of cytoplasmic transcription factors that mediate intracellular signaling that is usually generated at cell surface receptors and thereby transmit it to the nucleus. Numerous studies have demonstrated constitutive activation of STAT3 in a wide variety of human tumors, including hematological malignancies (leukemias, lymphomas, and multiple myeloma) as well as diverse solid tumors (such as head and neck, breast, lung, gastric, hepatocellular, colorectal and prostate cancers). There is strong evidence to suggest that aberrant STAT3 signaling promotes initiation and progression of human cancers by either inhibiting apoptosis or inducing cell proliferation, angiogenesis, invasion, and metastasis. Suppression of STAT3 activation results in the induction of apoptosis in tumor cells, and accordingly its pharmacological modulation by tyrosine kinase inhibitors, antisense oligonucleotides, decoy nucleotides, dominant negative proteins, RNA interference and chemopreventive agents have been employed to suppress the proliferation of various human cancer cells in culture and tumorigenicity in vivo. However, the identification and development of novel drugs that can target deregulated STAT3 activation effectively remains an important scientific and clinical challenge. This review presents the evidence for critical roles of STAT3 in oncogenesis and discusses the potential for development of novel cancer therapies based on mechanistic understanding of STAT3 signaling cascade.

Capillarisin inhibits constitutive and inducible STAT3 activation through induction of SHP-1 and SHP-2 tyrosine phosphatases

Signal transducers and activators of transcription (STAT)-3 is a latent cytosolic transcription factor that has been closely associated with survival, proliferation, chemoresistance, and metastasis of tumor cells. Whether the anti-proliferative, pro-apoptotic, and anti-metastatic effects of capillarisin (CPS), derived from Artemisia capillaris (Compositae), are linked to its capability to inhibit STAT3 activation was investigated. We found that CPS specifically inhibited both constitutive and inducible STAT3 activation at tyrosine residue 705 but not at serine residue 727 in human multiple myeloma cells. Besides the inhibition of STAT3 phosphorylation, CPS also abrogated STAT3 constitutive activity and nuclear translocation. The suppression of STAT3 was mediated through the inhibition of activation of upstream JAK1, JAK2, and c-Src kinases. Treatment with the protein tyrosine phosphatase (PTP) inhibitor pervanadate treatment reversed the CPS-induced down-regulation of JAK1/2 and STAT3, thereby suggesting the involvement of a PTP. Indeed, knockdown of the SHP-1 and SHP-2 genes by small interfering RNA suppressed the ability of CPS to inhibit JAK1 and STAT3 activation, suggesting the critical role of both SHP-1 and SHP-2 in its possible mechanism of action. CPS downregulated the expression of STAT3-regulated antiapoptotic and proliferative gene products; and this correlated with suppression of cell viability, the accumulation of cells in sub-G1 phase of cell cycle and induction of apoptosis. Moreover, CPS potentiated bortezomib-induced apoptotic effects in MM cells, and this correlated with down-regulation of various gene products that mediate cell proliferation (Cyclin D1 and COX-2), cell survival (Bcl-2, Bcl-xl, IAP1, IAP2, and Survivin), invasion (MMP-9), and angiogenesis (VEGF). Thus, overall, our results suggest that CPS is a novel blocker of STAT3 activation and thus may have a potential in negative regulation of growth, metastasis, and chemoresistance of tumor cells.

The Atlantic salmon protein tyrosine kinase Tyk2: molecular cloning, modulation of expression and function

Tyk2, a member of the Janus Kinase (JAK) family of protein tyrosine kinases, is required for interferon-α/β binding and signaling in higher vertebrates. Currently, little is known about the role of the different JAKs in signaling responses to interferon (IFN) in lower vertebrates including fish. In this paper we report the identification and characterization of Atlantic salmon (Salmo salar) Tyk2. Four cDNA sequences, two containing an open reading frame encoding full-length Tyk protein and two with an up-stream in frame stop codon, were identified. The deduced amino acid sequences of the salmon full-length Tyk2 proteins showed highest identity with Tyk2 from other species and their transcripts were ubiquitously expressed. Like in mammals the presented data suggests that salmon Tyk2 is auto-phosporylated when ectopically expressed in cells. In our experiments, full-length salmon Tyk2 overexpressed in CHSE-cells phosphorylated itself, while both a kinase-deficient mutant and the truncated Tyk2 (Tyk-short) were inactive. Interestingly, the overexpression of full length Tyk2 was shown to up-regulate the transcript levels of the IFN induced gene Mx, thus indicating the involvement of salmon Tyk2 in the salmon IFN I pathway.

The role of glycogen synthase kinase 3-β in immunity and cell cycle: implications in esophageal cancer

Esophageal cancer (EC) is one of the most aggressive gastrointestinal malignancies, possessing an insidious onset and a poor prognosis. Numerous transcription factors and inflammatory mediators have been reported to play a pivotal role in the initiation and progression of this cancer. However, the specifics of the signaling network responsible for said factors, especially which elements are the critical regulators, are still being elucidated. Glycogen synthesis kinases 3 (GSK3)β was originally regarded as a kinase regulating glucose metabolism. Accumulating evidence demonstrated that it also played an essential role in a variety of cellular processes including proliferation, differentiation, inflammation, motility, and survival by regulating various transcription factors such as c-Jun, AP-1, β-catenin, CREB, and NF-κB. Aberrant regulation of GSK3β has been shown to promote cell growth in some cancers, while suppressing it in others, and thus may play an important role in the development of EC. This review will discuss our current understanding of GSK3β signaling, and its control of the expression and activation of various transcription factors that mediate the inflammatory response. We will also explore some of the known mediators of EC progression, and based on current literature, elucidate the potential roles and implications of GSK3 in this disease.

Noise propagation through extracellular signaling leads to fluctuations in gene expression

BACKGROUND

Cell-to-cell variability in mRNA and proteins has been observed in many biological systems, including the human innate immune response to viral infection. Most of these studies have focused on variability that arises from (a) intrinsic stochastic fluctuations in gene expression and (b) extrinsic sources (e.g. fluctuations in transcription factors). The main focus of our study is the effect of extracellular signaling on enhancing intrinsic stochastic fluctuations. As a new source of noise, the communication between cells with fluctuating numbers of components has received little attention. We use agent-based modeling to study this contribution to noise in a system of human dendritic cells responding to viral infection.

RESULTS

Our results, validated by single-cell experiments, show that in the transient state cell-to-cell variability in an interferon-stimulated gene (DDX58) arises from the interplay between the spatial randomness of the cellular sources of the interferon and the temporal stochasticity of its own production. The numerical simulations give insight into the time scales on which autocrine and paracrine signaling act in a heterogeneous population of dendritic cells upon viral infection. We study the effect of different factors that influence the magnitude of the cell-to-cell-variability of the induced gene, including the cell density, multiplicity of infection, and the time scale over which the cellular sources begin producing the cytokine.

CONCLUSIONS

We propose a mechanism of noise propagation through extracellular communication and establish conditions under which the mechanism is operative. The cellular stochasticity of gene induction, which we investigate, is not limited to the specific interferon-induced gene we have studied; a broad distribution of copy numbers across cells is to be expected for other interferon-stimulated genes. This can lead to functional consequences for the system-level response to a viral challenge.

microRNA control of interferons and interferon induced anti-viral activity

Interferons (IFNs) are cytokines that are spontaneously produced in response to virus infection. They act by binding to IFN-receptors (IFN-R), which trigger JAK/STAT cell signalling and the subsequent induction of hundreds of IFN-inducible genes, including both protein-coding and microRNA genes. IFN-induced genes then act synergistically to prevent virus replication and create an anti-viral state. miRNA are therefore integral to the innate response to virus infection and are important components of IFN-mediated biology. On the other hand viruses also encode miRNAs that in some cases interfere directly with the IFN response to infection. This review summarizes the important roles of miRNAs in virus infection acting both as IFN-stimulated anti-viral molecules and as critical regulators of IFNs and IFN-stimulated genes. It also highlights how recent knowledge in RNA editing influence miRNA control of virus infection.

Palmitate induces transcriptional regulation of BACE1 and presenilin by STAT3 in neurons mediated by astrocytes

Deregulation of calcium has been implicated in neurodegenerative diseases, including Alzheimer's disease (AD). Previously, we showed that saturated free-fatty acid, palmitate, causes AD-like changes in primary cortical neurons mediated by astrocytes. However, the molecular mechanisms by which conditioned medium from astrocytes cultured in palmitate induce AD-like changes in neurons are unknown. This study demonstrates that this condition medium from astrocytes elevates calcium level in the neurons, which subsequently increases calpain activity, a calcium-dependent protease, leading to enhance p25/Cdk5 activity and phosphorylation and activation of the STAT3 (signal transducer and activator of transcription) transcription factor. Inhibiting calpain or Cdk5 significantly reduces the upregulation in nuclear level of pSTAT3, which we found to transcriptionally regulate both BACE1 and presenilin-1, the latter is a catalytic subunit of γ-secretase. Decreasing pSTAT3 levels reduced the mRNA levels of both BACE1 and presenilin-1 to near control levels. These data demonstrate a signal pathway leading to the activation of STAT3, and the generation of the amyloid peptide. Thus, our results suggest that STAT3 is an important potential therapeutic target of AD pathogenesis.

Low level methylmercury enhances CNTF-evoked STAT3 signaling and glial differentiation in cultured cortical progenitor cells

Although many previous investigations have studied how mercury compounds cause cell death, sub-cytotoxic levels may affect mechanisms essential for the proper development of the nervous system. The present study investigates whether low doses of methylmercury (MeHg) and mercury chloride (HgCl2) can modulate the activity of JAK/STAT signaling, a pathway that promotes gliogenesis. We report that sub-cytotoxic doses of MeHg enhance ciliary neurotrophic factor (CNTF) evoked STAT3 phosphorylation in human SH-SY5Y neuroblastoma and mouse cortical neural progenitor cells (NPCs). This effect is specific for MeHg, since HgCl2 fails to enhance JAK/STAT signaling. Exposing NPCs to these low doses of MeHg (30-300nM) enhances CNTF-induced expression of STAT3-target genes such as glial fibrillary acidic protein (GFAP) and suppressors of cytokine signaling 3 (SOCS3), and increases the proportion of cells expressing GFAP following 2 days of differentiation. Higher, near-cytotoxic concentrations of MeHg and HgCl2 inhibit STAT3 phosphorylation and lead to increased production of superoxide. Lower concentrations of MeHg effective in enhancing JAK/STAT signaling (30nM) do not result in a detectable increase in superoxide nor increased expression of the oxidant-responsive genes, heme oxygenase 1, heat shock protein A5 and sirtuin 1. These findings suggest that low concentrations of MeHg inappropriately enhance STAT3 phosphorylation and glial differentiation, and that the mechanism causing this enhancement is distinct from the reactive oxygen species-associated cell death observed at higher concentrations of MeHg and HgCl2.

Rotavirus NSP1 mediates degradation of interferon regulatory factors through targeting of the dimerization domain

Rotavirus nonstructural protein NSP1 can inhibit expression of interferon (IFN) and IFN-stimulated gene products by inducing proteasome-mediated degradation of IFN-regulatory factors (IRFs), including IRF3, IRF5, and IRF7. All IRF proteins share an N-terminal DNA-binding domain (DBD), and IRF3, IRF5, and IRF7 contain a similar C-proximal IRF association domain (IAD) that mediates IRF dimerization. An autoinhibitory domain (ID) at the extreme C terminus interacts with the IAD, burying residues necessary for IRF dimerization. Phosphorylation of serine/threonine residues in the ID induces charge repulsions that unmask the IAD, enabling IRF dimerization and subsequent nuclear translocation. To define the region of IRF proteins targeted for degradation by NSP1, we generated IRF3 and IRF7 truncation mutants and transiently expressed each with simian SA11-4F NSP1. These assays indicated that the IAD represented a necessary and sufficient target for degradation. Because NSP1 did not mediate degradation of truncated forms of the IAD, NSP1 likely requires a structurally intact IAD for recognition and targeting of IRF proteins. IRF9, which contains an IAD-like region that directs interactions with signal inducer and activator of transcription (STAT) proteins, was also targeted for degradation by NSP1, while IRF1, which lacks an IAD, was not. Analysis of mutant forms of IRF3 unable to undergo dimerization or that were constitutively dimeric showed that both were targeted for degradation by NSP1. These results indicate that SA11-4F NSP1 can induce degradation of inactive and activated forms of IAD-containing IRF proteins (IRF3 to IRF9), allowing a multipronged attack on IFN-based pathways that promote antiviral innate and adaptive immune responses.

Garcinol, a polyisoprenylated benzophenone modulates multiple proinflammatory signaling cascades leading to the suppression of growth and survival of head and neck carcinoma

Constitutive activation of proinflammatory transcription factors such as STAT3 and NF-κB plays a pivotal role in the proliferation and survival of squamous cell carcinoma of the head and neck (HNSCC). Thus, the agents that can modulate deregulated STAT3 and NF-κB activation have a great potential both for the prevention and treatment of HNSCC. In the present report, we investigated the potential effects of garcinol, an active component of Garcinia indica on various inflammatory mediators involved in HNSCC progression using cell lines and xenograft mouse model. We found that garcinol inhibited constitutively activated STAT3 in HNSCC cells in a time- and dose-dependent manner, which correlated with the suppression of the upstream kinases (c-Src, JAK1, and JAK2) in HNSCC cells. Also, we noticed that the generation of reactive oxygen species is involved in STAT3 inhibitory effect of garcinol. Furthermore, garcinol exhibited an inhibitory effect on the constitutive NF-κB activation, mediated through the suppression of TGF-β-activated kinase 1 (TAK1) and inhibitor of IκB kinase (IKK) activation in HNSCC cells. Garcinol also downregulated the expression of various gene products involved in proliferation, survival, and angiogenesis that led to the reduction of cell viability and induction of apoptosis in HNSCC cells. When administered intraperitoneally, garcinol inhibited the growth of human HNSCC xenograft tumors in male athymic nu/nu mice. Overall, our results suggest for the first time that garcinol mediates its antitumor effects in HNSCC cells and mouse model through the suppression of multiple proinflammatory cascades.

Lead identification of novel and selective TYK2 inhibitors

A therapeutic rationale is proposed for the treatment of inflammatory diseases, such as psoriasis and inflammatory bowel diseases (IBD), by selective targeting of TYK2. Hit triage, following a high-throughput screen for TYK2 inhibitors, revealed pyridine 1 as a promising starting point for lead identification. Initial expansion of 3 separate regions of the molecule led to eventual identification of cyclopropyl amide 46, a potent lead analog with good kinase selectivity, physicochemical properties, and pharmacokinetic profile. Analysis of the binding modes of the series in TYK2 and JAK2 crystal structures revealed key interactions leading to good TYK2 potency and design options for future optimization of selectivity.