Interferon-γ engages the p70 S6 kinase to regulate phosphorylation of the 40S S6 ribosomal protein

Cardioprotective microRNAs (protectomiRs) in a pig model of acute myocardial infarction and cardioprotection by ischaemic conditioning: MiR-450a

BACKGROUND AND PURPOSE

Cardioprotective miRNAs (protectomiRs) are promising therapeutic tools. Here, we aimed to identify protectomiRs in a translational porcine model of acute myocardial infarction (AMI) and to validate their cardiocytoprotective effect.

EXPERIMENTAL APPROACH

ProtectomiR candidates were selected after systematic analysis of miRNA expression changes in cardiac tissue samples from a closed-chest AMI model in pigs subjected to sham operation, AMI and ischaemic preconditioning, postconditioning or remote preconditioning, respectively. Cross-species orthologue protectomiR candidates were validated in simulated ischaemia-reperfusion injury (sI/R) model of isolated rat ocardiomyocytes and in human AC16 cells as well. For miR-450a, we performed target prediction and analysed the potential mechanisms of action by GO enrichment and KEGG pathway analysis.

KEY RESULTS

Out of the 220 detected miRNAs, four were up-regulated and 10 were down-regulated due to all three conditionings versus AMI. MiR-450a and miR-451 mimics at 25 nM were protective in rat cardiomyocytes, and miR-450a showed protection in human cardiomyocytes as well. MiR-450a has 3987 predicted mRNA targets in pigs, 4279 in rats and 8328 in humans. Of these, 607 genes are expressed in all three species. A total of 421 common enriched GO terms were identified in all three species, whereas KEGG pathway analysis revealed 13 common pathways.

CONCLUSION AND IMPLICATIONS

This is the first demonstration that miR-450a is associated with cardioprotection by ischaemic conditioning in a clinically relevant porcine model and shows cardiocytoprotective effect in human cardiomyocytes, making it a promising drug candidate. The mechanism of action of miR-450a involves multiple cardioprotective pathways.

Translation Inhibition Mediated by Interferon-Stimulated Genes during Viral Infections

Viruses often pose a significant threat to the host through the exploitation of cellular machineries for their own benefit. In the context of immune responses, myriad host factors are deployed to target viral RNAs and inhibit viral protein translation, ultimately hampering viral replication. Understanding how "non-self" RNAs interact with the host translation machinery and trigger immune responses would help in the development of treatment strategies for viral infections. In this review, we explore how interferon-stimulated gene products interact with viral RNA and the translation machinery in order to induce either global or targeted translation inhibition.

The crucial regulatory role of type I interferon in inflammatory diseases

Type I interferon (IFN-I) plays crucial roles in the regulation of inflammation and it is associated with various inflammatory diseases including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and periodontitis, impacting people's health and quality of life. It is well-established that IFN-Is affect immune responses and inflammatory factors by regulating some signaling. However, currently, there is no comprehensive overview of the crucial regulatory role of IFN-I in distinctive pathways as well as associated inflammatory diseases. This review aims to provide a narrative of the involvement of IFN-I in different signaling pathways, mainly mediating the related key factors with specific targets in the pathways and signaling cascades to influence the progression of inflammatory diseases. As such, we suggested that IFN-Is induce inflammatory regulation through the stimulation of certain factors in signaling pathways, which displays possible efficient treatment methods and provides a reference for the precise control of inflammatory diseases.

Diagnostic Predictors of Immunotherapy Response in Head and Neck Squamous Cell Carcinoma

Programmed cell death ligand-1 (PD-L1) binds PD-1 on CD⁸⁺ lymphocytes, inhibiting their cytotoxic action. Its aberrant expression by head and neck squamous cell carcinoma (HNSCC) cells leads to immune escape. Pembrolizumab and nivolumab, two humanized monoclonal antibodies against PD-1, have been approved in HNSCC treatment, but ~60% of patients with recurrent or metastatic HNSCC fail to respond to immunotherapy and only 20 to 30% of treated patients have long-term benefits. The purpose of this review is to analyze all the fragmentary evidence present in the literature to identify what future diagnostic markers could be useful for predicting, together with PD-L1 CPS, the response to immunotherapy and its durability. We searched PubMed, Embase, and the Cochrane Register of Controlled Trials and we summarize the evidence collected in this review. We confirmed that PD-L1 CPS is a predictor of response to immunotherapy, but it should be measured across multiple biopsies and repeatedly over time. PD-L2, IFN-γ, EGFR, VEGF, TGF-β, TMB, blood TMB, CD73, TILs, alternative splicing, tumor microenvironment, and some macroscopic and radiological features are promising predictors worthy of further studies. Studies comparing predictors appear to give greater potency to TMB and CXCR9.

Interferon regulates neural stem cell function at all ages by orchestrating mTOR and cell cycle

Stem cells show intrinsic interferon signalling, which protects them from viral infections at all ages. In the ageing brain, interferon signalling also reduces the ability of stem cells to activate. Whether these functions are linked and at what time interferons start taking on a role in stem cell functioning is unknown. Additionally, the molecular link between interferons and activation in neural stem cells and how this relates to progenitor production is not well understood. Here we combine single-cell transcriptomics, RiboSeq and mathematical models of interferon to show that this pathway is important for proper stem cell function at all ages in mice. Interferon orchestrates cell cycle and mTOR activity to post-transcriptionally repress Sox2 and induces quiescence. The interferon response then decreases in the subsequent maturation states. Mathematical simulations indicate that this regulation is beneficial for the young and harmful for the old brain. Our study establishes molecular mechanisms of interferon in stem cells and interferons as genuine regulators of stem cell homeostasis and a potential therapeutic target to repair the ageing brain.

Programmed Cell Death-Ligand 1 in Head and Neck Squamous Cell Carcinoma: Molecular Insights, Preclinical and Clinical Data, and Therapies

Aberrant expression of the programmed cell death protein ligand 1 (PD-L1) constitutes one of the main immune evasion mechanisms of cancer cells. The approval of drugs against the PD-1-PD-L1 axis has given new impetus to the chemo-therapy of many malignancies. We performed a literature review from 1992 to August 2022, summarizing evidence regarding molecular structures, physiological and pathological roles, mechanisms of PD-L1 overexpression, and immunotherapy evasion. Furthermore, we summarized the studies concerning head and neck squamous cell carcinomas (HNSCC) immunotherapy and the prospects for improving the associated outcomes, such as identifying treatment response biomarkers, new pharmacological combinations, and new molecules. PD-L1 overexpression can occur via four mechanisms: genetic modifications; inflammatory signaling; oncogenic pathways; microRNA or protein-level regulation. Four molecular mechanisms of resistance to immunotherapy have been identified: tumor cell adaptation; changes in T-cell function or proliferation; alterations of the tumor microenvironment; alternative immunological checkpoints. Immunotherapy was indeed shown to be superior to traditional chemotherapy in locally advanced/recurrent/metastatic HNSCC treatments.

Slippy-Sloppy translation: a tale of programmed and induced-ribosomal frameshifting

Programmed ribosomal frameshifting (PRF) is a key mechanism that viruses use to generate essential proteins for replication, and as a means of regulating gene expression. PRF generally involves recoding signals or frameshift stimulators to elevate the occurrence of frameshifting at shift-prone 'slippery' sequences. Given its essential role in viral replication, targeting PRF was envisioned as an attractive tool to block viral infection. However, in contrast to controlled-PRF mechanisms, recent studies have shown that ribosomes of many human cancer cell types are prone to frameshifting upon amino acid shortage; thus, these cells are deemed to be sloppy. The resulting products of a sloppy frameshift at the 'hungry' codons are aberrant proteins the degradation and display of which at the cell surface can trigger T cell activation. In this review, we address recent discoveries in ribosomal frameshifting and their functional consequences for the proteome in human cancer cells.

Generation, secretion and degradation of cancer immunotherapy target PD-L1

Cancer immunotherapy is a rapidly developing and effective method for the treatment of a variety of malignancies in recent years. As a significant immune checkpoint, programmed cell death 1 ligand 1 (PD-L1) and its receptor programmed cell death protein 1 (PD-1) play the most significant role in cancer immune escape and cancer immunotherapy. Though PD-L1 have become an important target for drug development and there have been various approved drugs and clinic trials targeting it, and various clinical response rate and adverse reactions prevent many patients from benefiting from it. In recent years, combination trials have become the main direction of PD-1/PD-L1 antibodies development. Here, we summarized PD-L1 biofunctions and key roles in various cancers along with the development of PD-L1 inhibitors. The regulators that are involved in controlling PD-L1 expression including post-translational modification, mRNA level regulation as well as degradation and exosome secretory pathway of PD-L1 were focused. This systematic summary may provide comprehensive understanding of different regulations on PD-L1 as well as a broad prospect for the search of the important regulator of PD-L1. The regulatory factors of PD-L1 can be potential targets for immunotherapy and increase strategies of immunotherapy in combination.

Interferon Alpha Induces Cellular Autophagy and Modulates Hepatitis B Virus Replication

Hepatitis B virus (HBV) infection causes acute and chronic liver diseases, including severe hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC). Interferon alpha 2a (IFNα-2a) is commonly used for treating chronic HBV infection. However, its efficacy remains relatively low. Yet, the immunological and molecular mechanisms for successful IFNα-2a treatment remain elusive. One issue is whether the application of increasing IFNα doses may modulate cellular processes and HBV replication in hepatic cells. In the present study, we focused on the interaction of IFNα signaling with other cellular signaling pathways and the consequence for HBV replication. The results showed that with the concentration of 6000 U/ml IFNα-2a treatment downregulated the activity of not only the Akt/mTOR signaling but also the AMPK signaling. Additionally, IFNα-2a treatment increased the formation of the autophagosomes by blocking autophagic degradation. Furthermore, IFNα-2a treatment inhibited the Akt/mTOR signaling and initiated autophagy under low and high glucose concentrations. In reverse, inhibition of autophagy using 3-methyladenine (3-MA) and glucose concentrations influenced the expression of IFNα-2a-induced ISG15 and IFITM1. Despite of ISGs induction, HBV replication and gene expression in HepG2.2.15 cells, a cell model with continuous HBV replication, were slightly increased at high doses of IFNα-2a. In conclusion, our study indicates that IFNα-2a treatment may interfere with multiple intracellular signaling pathways, facilitate autophagy initiation, and block autophagic degradation, thereby resulting in slightly enhanced HBV replication.

Functional analysis and regulation mechanism of interferon gamma in macrophages of large yellow croaker (Larimichthys crocea)

Interferon gamma (IFN-γ) is a widely expressed cytokine that has potent antiviral and immunomodulatory effects. The expression and bioactivity of IFN-γ have been reported in several fish species. However, the molecular mechanism mediated by IFN-γ in fish macrophages has not been completely elucidated. This study used the macrophage cell line to investigate the functional activities and regulation mechanism of large yellow croaker IFN-γ (LcIFN-γ). Herein, the mRNA expression of Lcifn-γ was significantly upregulated in macrophages after LPS and poly(I:C) treatment. Recombinant LcIFN-γ protein (rLcIFN-γ) significantly enhanced the phagocytic ability and respiratory burst activity of macrophages. Meanwhile, rLcIFN-γ induced M1 phenotype polarization of macrophages with the upregulated expressions of pro-inflammatory gene. Moreover, rLcIFN-γ upregulated the IFN-stimulated genes (ISGs) expression and activated JAK (Janus tyrosine kinases)-STAT (signal transducer and activator of transcription) signaling pathway by causing the phosphorylation of JAK1 and STAT1^Tyr701. Furthermore, the promoter activity of IFN-regulatory factor 1 (IRF1) was significantly upregulated by the phosphorylated transcription factor STAT1 through binding to its promoter region. In addition to the classical JAK-STAT pathway, rLcIFN-γ also activated multiple distinct signaling cascades such as mitogen-activated protein kinase (MAPK) and protein kinase B (AKT) pathways. Overall, this study indicated the powerful effects of LcIFN-γ on macrophage activation of large yellow croaker and its molecular mechanism.

mTOR Signaling: The Interface Linking Cellular Metabolism and Hepatitis B Virus Replication

Mammalian target of rapamycin (mTOR) is a conserved Ser/Thr kinase that includes mTOR complex (mTORC) 1 and mTORC2. The mTOR pathway is activated in viral hepatitis, including hepatitis B virus (HBV) infection-induced hepatitis. Currently, chronic HBV infection remains one of the most serious public health issues worldwide. The unavailability of effective therapeutic strategies for HBV suggests that clarification of the pathogenesis of HBV infection is urgently required. Increasing evidence has shown that HBV infection can activate the mTOR pathway, indicating that HBV utilizes or hijacks the mTOR pathway to benefit its own replication. Therefore, the mTOR signaling pathway might be a crucial target for controlling HBV infection. Here, we summarize and discuss the latest findings from model biology research regarding the interaction between the mTOR signaling pathway and HBV replication.

IFNs Reset the Differential Capacity of Human Monocyte Subsets to Produce IL-12 in Response to Microbial Stimulation

Human primary monocytes are composed of a minor, more mature CD16+(CD14low/neg) population and a major CD16neg(CD14+) subset. The specific functions of CD16+ versus CD16neg monocytes in steady state or inflammation remain poorly understood. In previous work, we found that IL-12 is selectively produced by the CD16+ subset in response to the protozoan pathogen, Toxoplasma gondii In this study, we demonstrated that this differential responsiveness correlates with the presence of an IFN-induced transcriptional signature in CD16+ monocytes already at baseline. Consistent with this observation, we found that in vitro IFN-γ priming overcomes the defect in the IL-12 response of the CD16neg subset. In contrast, pretreatment with IFN-γ had only a minor effect on IL-12p40 secretion by the CD16+ population. Moreover, inhibition of the mTOR pathway also selectively increased the IL-12 response in CD16neg but not in CD16+ monocytes. We further demonstrate that in contrast to IFN-γ, IFN-α fails to promote IL-12 production by the CD16neg subset and blocks the effect of IFN-γ priming. Based on these observations, we propose that the acquisition of IL-12 responsiveness by peripheral blood monocyte subsets depends on extrinsic signals experienced during their developmental progression in vivo. This process can be overridden during inflammation by the opposing regulatory effects of type I and II IFN as well as the mTOR inhibition.

Actionable Cytopathogenic Host Responses of Human Alveolar Type 2 Cells to SARS-CoV-2

Human transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causative pathogen of the COVID-19 pandemic, exerts a massive health and socioeconomic crisis. The virus infects alveolar epithelial type 2 cells (AT2s), leading to lung injury and impaired gas exchange, but the mechanisms driving infection and pathology are unclear. We performed a quantitative phosphoproteomic survey of induced pluripotent stem cell-derived AT2s (iAT2s) infected with SARS-CoV-2 at air-liquid interface (ALI). Time course analysis revealed rapid remodeling of diverse host systems, including signaling, RNA processing, translation, metabolism, nuclear integrity, protein trafficking, and cytoskeletal-microtubule organization, leading to cell cycle arrest, genotoxic stress, and innate immunity. Comparison to analogous data from transformed cell lines revealed respiratory-specific processes hijacked by SARS-CoV-2, highlighting potential novel therapeutic avenues that were validated by a high hit rate in a targeted small molecule screen in our iAT2 ALI system.

Roles of IFN-γ in tumor progression and regression: a review

BACKGROUND

Interferon-γ (IFN-γ) plays a key role in activation of cellular immunity and subsequently, stimulation of antitumor immune-response. Based on its cytostatic, pro-apoptotic and antiproliferative functions, IFN-γ is considered potentially useful for adjuvant immunotherapy for different types of cancer. Moreover, it IFN-γ may inhibit angiogenesis in tumor tissue, induce regulatory T-cell apoptosis, and/or stimulate the activity of M1 proinflammatory macrophages to overcome tumor progression. However, the current understanding of the roles of IFN-γ in the tumor microenvironment (TME) may be misleading in terms of its clinical application.

MAIN BODY

Some researchers believe it has anti-tumorigenic properties, while others suggest that it contributes to tumor growth and progression. In our recent work, we have shown that concentration of IFN-γ in the TME determines its function. Further, it was reported that tumors treated with low-dose IFN-γ acquired metastatic properties while those infused with high dose led to tumor regression. Pro-tumorigenic role may be described through IFN-γ signaling insensitivity, downregulation of major histocompatibility complexes, upregulation of indoleamine 2,3-dioxygenase, and checkpoint inhibitors such as programmed cell death ligand 1.

CONCLUSION

Significant research efforts are required to decipher IFN-γ-dependent pro- and anti-tumorigenic effects. This review discusses the current knowledge concerning the roles of IFN-γ in the TME as a part of the complex immune response to cancer and highlights the importance of identifying IFN-γ responsive patients to improve their sensitivity to immuno-therapies.

The Global Phosphorylation Landscape of SARS-CoV-2 Infection

The causative agent of the coronavirus disease 2019 (COVID-19) pandemic, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has infected millions and killed hundreds of thousands of people worldwide, highlighting an urgent need to develop antiviral therapies. Here we present a quantitative mass spectrometry-based phosphoproteomics survey of SARS-CoV-2 infection in Vero E6 cells, revealing dramatic rewiring of phosphorylation on host and viral proteins. SARS-CoV-2 infection promoted casein kinase II (CK2) and p38 MAPK activation, production of diverse cytokines, and shutdown of mitotic kinases, resulting in cell cycle arrest. Infection also stimulated a marked induction of CK2-containing filopodial protrusions possessing budding viral particles. Eighty-seven drugs and compounds were identified by mapping global phosphorylation profiles to dysregulated kinases and pathways. We found pharmacologic inhibition of the p38, CK2, CDK, AXL, and PIKFYVE kinases to possess antiviral efficacy, representing potential COVID-19 therapies.

Interferon signaling in cancer. Non-canonical pathways and control of intracellular immune checkpoints

The interferons (IFNs) are cytokines with important antineoplastic and immune modulatory effects. These cytokines have been conserved through evolution as important elements of the immune surveillance against cancer. Despite this, defining their precise and specific roles in the generation of antitumor responses remains challenging. Emerging evidence suggests the existence of previously unknown roles for IFNs in the control of the immune response against cancer that may redefine our understanding on how these cytokines function. Beyond the engagement of classical JAK-STAT signaling pathways that promote transcription and expression of gene products, the IFNs engage multiple other signaling cascades to generate products that mediate biological responses and outcomes. There is recent emerging evidence indicating that IFNs control the expression of both traditional immune checkpoints like the PD-L1/PD1 axis, but also less well understood "intracellular" immune checkpoints whose targeting may define new approaches for the treatment of malignancies.

Regulation and Function of the PD-L1 Checkpoint

Expression of programmed death-ligand 1 (PD-L1) is frequently observed in human cancers. Binding of PD-L1 to its receptor PD-1 on activated T cells inhibits anti-tumor immunity by counteracting T cell-activating signals. Antibody-based PD-1-PD-L1 inhibitors can induce durable tumor remissions in patients with diverse advanced cancers, and thus expression of PD-L1 on tumor cells and other cells in the tumor microenviroment is of major clinical relevance. Here we review the roles of the PD-1-PD-L1 axis in cancer, focusing on recent findings on the mechanisms that regulate PD-L1 expression at the transcriptional, posttranscriptional, and protein level. We place this knowledge in the context of observations in the clinic and discuss how it may inform the design of more precise and effective cancer immune checkpoint therapies.

P21-activated kinase 2 is essential in maintenance of peripheral Foxp3+ regulatory T cells

The p21‐activated kinase 2 (Pak2), an effector molecule of the Rho family GTPases Rac and Cdc42, regulates diverse functions of T cells. Previously, we showed that Pak2 is required for development and maturation of T cells in the thymus, including thymus‐derived regulatory T (Treg) cells. However, whether Pak2 is required for the functions of various subsets of peripheral T cells, such as naive CD4 and helper T‐cell subsets including Foxp3⁺ Treg cells, is unknown. To determine the role of Pak2 in CD4 T cells in the periphery, we generated inducible Pak2 knockout (KO) mice, in which Pak2 was deleted in CD4 T cells acutely by administration of tamoxifen. Temporal deletion of Pak2 greatly reduced the number of Foxp3⁺ Treg cells, while minimally affecting the homeostasis of naive CD4 T cells. Pak2 was required for proliferation and Foxp3 expression of Foxp3⁺ Treg cells upon T‐cell receptor and interleukin‐2 stimulation, differentiation of in vitro induced Treg cells, and activation of naive CD4 T cells. Together, Pak2 is essential in maintaining the peripheral Treg cell pool by providing proliferation and maintenance signals to Foxp3⁺ Treg cells.

Interferon gamma boosts the nucleotide oligomerization domain 2-mediated signaling pathway in human dendritic cells in an X-linked inhibitor of apoptosis protein and mammalian target of rapamycin-dependent manner

The cytoplasmic nucleotide oligomerization domain 2 (NOD2) receptor recognizes the bacterial cell wall component muramyl dipeptide (MDP). NOD2 ligation initiates the nuclear factor kappa B and the mitogen-activated protein kinase cascades. However, administering MDP alone is insufficient to elicit strong cytokine responses in various immune cells, including dendritic cells (DCs). Because the simultaneous presence of various microbial products and cytokines in inflamed tissues modulates DC function, we initiated this study to examine how interferon gamma (IFNγ), a central modulator of inflammation, affects the NOD2-mediated signaling pathway in human conventional DCs (cDCs). Synergistic stimulation of DCs with MDP and IFNγ increased the expression of CD40, CD80, CD83, CD86, and human leukocyte antigen DQ proteins and significantly elevated the production of pro-inflammatory cytokines IL-1β, IL-6, IL-12, and tumour necrosis factor (TNF), as well as anti-inflammatory cytokine IL-10. Furthermore, the simultaneous presence of MDP and IFNγ was necessary to decrease IkBα protein levels. By investigating various mechanisms implicated in MDP- and IFNγ-mediated signaling pathways, we revealed that the increased production of pro-inflammatory cytokines is highly dependent on the X-linked inhibitor of apoptosis protein (XIAP) but not on cellular IAP1 and IAP2. We also found that the NOD2 signaling pathway is regulated by the mammalian target of rapamycin (mTOR) but is not affected by phosphatidylinositol-3 kinase or signal transducer and activator of transcription 1 inhibition. Our results demonstrate, for the first time, that IFNγ positively affects NOD2-mediated signaling in human cDCs, in a manner considerably dependent on XIAP and partially dependent on mTOR.

CCR5-Dependent Activation of mTORC1 Regulates Translation of Inducible NO Synthase and COX-2 during Encephalomyocarditis Virus Infection

Encephalomyocarditis virus (EMCV) infection of macrophages results in the expression of a number of inflammatory and antiviral genes, including inducible NO synthase (iNOS) and cyclooxygenase (COX)-2. EMCV-induced macrophage activation has been shown to require the presence of CCR5 and the activation of PI3K-dependent signaling cascades. The purpose of this study was to determine the role of PI3K in regulating the macrophage responses to EMCV. We show that PI3K regulates EMCV-stimulated iNOS and COX-2 expression by two independent mechanisms. In response to EMCV infection, Akt is activated and regulates the translation of iNOS and COX-2 through the mammalian target of rapamycin complex (mTORC)1. The activation of mTORC1 during EMCV infection is CCR5-dependent and appears to function in a manner that promotes the translation of iNOS and COX-2. CCR5-dependent mTORC1 activation functions as an antiviral response, as mTORC1 inhibition increases the expression of EMCV polymerase. PI3K also regulates the transcriptional induction of iNOS and COX-2 in response to EMCV infection by a mechanism that is independent of Akt and mTORC1 regulation. These findings indicate that macrophage expression of the inflammatory genes iNOS and COX-2 occurs via PI3K- and Akt-dependent translational control of mTORC1 and PI3K-dependent, Akt-independent transcriptional control.

PLD1 activation mediates Amb a 1-induced Th2-associated cytokine expression via the JNK/ATF-2 pathway in BEAS-2B cells

The purpose of this study was to identify the role of phospholipase D1 (PLD1) in Amb a 1-induced IL-5 and IL-13 expression. When BEAS-2B cells were stimulated with Amb a 1, PLD activity increased, and knockdown of PLD1 decreased Amb a 1-induced IL-5 and IL-13 expression. Amb a 1 also activated the PLCγ/p70S6K/JNK pathway. Furthermore, Amb a 1-induced PLD activation was also attenuated by PLCγ inhibition, and knockdown of PLD1 decreased Amb a 1-induced activation of P70S6K and JNK. When ATF-2 activity was blocked with ATF-2 siRNA, Amb a 1-induced IL-5 and IL-13 expression was completely abolished, indicating that ATF-2 is a transcriptional factor required for the expression of IL-5 and IL-13 in response to Amb a 1. Taken together, we suggest that PLD1 acts as an important regulator in Amb a 1-induced expression of IL-5 and IL-13 via a PLCγ/p70S6K/JNK/ATF-2 pathway in BEAS-2B cells.

IFN-γ regulates CD8+ memory T cell differentiation and survival in response to weak, but not strong, TCR signals

In response to primary Ag contact, naive mouse CD8(+) T cells undergo clonal expansion and differentiate into effector T cells. After pathogen clearance, most effector T cells die, and only a small number of memory T cell precursors (TMPs) survive to form a pool of long-lived memory T cells (TMs). Although high- and low-affinity CD8(+) T cell clones are recruited into the primary response, the TM pool consists mainly of high-affinity clones. It remains unclear whether the more efficient expansion of high-affinity clones and/or cell-intrinsic processes exclude low-affinity T cells from the TM pool. In this article, we show that the lack of IFN-γR signaling in CD8(+) T cells promotes TM formation in response to weak, but not strong, TCR agonists. The IFN-γ-sensitive accumulation of TMs correlates with reduced mammalian target of rapamycin activation and the accumulation of long-lived CD62L(hi)Bcl-2(hi)Eomes(hi) TMPs. Reconstitution of mammalian target of rapamycin or IFN-γR signaling is sufficient to block this process. Hence, our data suggest that IFN-γR signaling actively blocks the formation of TMPs responding to weak TCR agonists, thereby promoting the accumulation of high-affinity T cells finally dominating the TM pool.

Deficiency in either 4E-BP1 or 4E-BP2 augments innate antiviral immune responses

Genetic deletion of both 4E-BP1 and 4E-BP2 was found to protect cells against viral infections. Here we demonstrate that the individual loss of either 4E-BP1 or 4E-BP2 in mouse embryonic fibroblasts (MEFs) is sufficient to confer viral resistance. shRNA-mediated silencing of 4E-BP1 or 4E-BP2 renders MEFs resistant to viruses, and compared to wild type cells, MEFs knockout for either 4E-BP1 or 4E-BP2 exhibit enhanced translation of Irf-7 and consequently increased innate immune response to viruses. Accordingly, the replication of vesicular stomatitis virus, encephalomyocarditis virus, influenza virus and Sindbis virus is markedly suppressed in these cells. Importantly, expression of either 4E-BP1 or 4E-BP2 in double knockout or respective single knockout cells diminishes their resistance to viral infection. Our data show that loss of 4E-BP1 or 4E-BP2 potentiates innate antiviral immunity. These results provide further evidence for translational control of innate immunity and support targeting translational effectors as an antiviral strategy.

Interferon receptor signaling in malignancy: a network of cellular pathways defining biological outcomes

IFNs are cytokines with important antiproliferative activity and exhibit key roles in immune surveillance against malignancies. Early work initiated over three decades ago led to the discovery of IFN receptor activated Jak-Stat pathways and provided important insights into mechanisms for transcriptional activation of IFN-stimulated genes (ISG) that mediate IFN biologic responses. Since then, additional evidence has established critical roles for other receptor-activated signaling pathways in the induction of IFN activities. These include MAPK pathways, mTOR cascades, and PKC pathways. In addition, specific miRNAs appear to play a significant role in the regulation of IFN signaling responses. This review focuses on the emerging evidence for a model in which IFNs share signaling elements and pathways with growth factors and tumorigenic signals but engage them in a distinctive manner to mediate antiproliferative and antiviral responses.

Leptin increases TNF-α expression and production through phospholipase D1 in Raw 264.7 cells

Epidemiological evidence suggests that obesity is associated with inflammation of the respiratory tract and the pathogenesis of asthma. The purpose of this study was to examine the role of phospholipase D1 (PLD1) in leptin-induced expression of the proinflammatory cytokine, tumor necrosis factor (TNF)-α, and to suggest a molecular link between obesity and respiratory tract inflammation. We investigated whether leptin, a typical adipocytokine, plays a role in the expression of TNF-α through increased PLD1 activity in Raw 264.7. Leptin enhanced the activity of PLD1 through activation of PLCγ and Src, while PLD1 siRNA decreased the leptin-induced expression and production of TNF-α. Leptin-induced PLD activation was also inhibited by a PLCγ inhibitor (PAO) and Src kinase inhibitor (PP2), indicating that PLCγ and Src kinase are upstream activators of PLD1. Down-regulation of PLD1 also completely blocked activation of p70S6K, an activator of JNK. Leptin-induced expression of TNF-α was also prevented by inhibition of p70S6K and JNK. Taken together, these results indicate that PLD1 acts as an important regulator of leptin-induced expression of TNF-α by participating in the PLCγ/Src/PLD1/PA/p70S6K/JNK pathway.

Inhibitory effect of 10-hydroxydecanoic acid on lipopolysaccharide-induced nitric oxide production via translational downregulation of interferon regulatory factor-1 in RAW264 murine macrophages

Toll-like receptors (TLRs) play a critical role in innate immunity by recognizing pathogen-associated molecular patterns. Various environmental materials including lipids may affect TLR signaling and modulate innate immune responses. We previously reported that 10-hydroxy-trans-2-decenoic acid (10H2DA) inhibits lipopolysaccharide (LPS)-induced interleukin (IL)-6 and nitric oxide (NO) production via inhibiting NF-κB activation. In this study, we investigated the effect of 10-hydroxydecanoic acid (10HDA), a saturated fatty acid of 10H2DA, on LPS-induced cytokines/chemokines and NO production. 10HDA inhibited LPS-induced NO production, but not tumor necrosis factor-α or IL-6 production. LPS-induced activation of interferon (IFN)-stimulated response element, but not NF-κB, was inhibited by 10HDA. Phosphorylation of STAT1 and STAT2 was not affected, but IFN-regulatory factor (IRF)-1 production was significantly reduced by 10HDA. The LPS-induced increase of IRF-1 mRNA, however, was not affected by 10HDA. We found that IRF-1 mRNA level in the polysomal fraction was significantly decreased by 10HDA. Further, LPS-induced phosphorylation of Akt and 4E-BP1, which control mRNA translation, was markedly decreased. These results suggest that 10HDA inhibited LPS-induced NO production through inhibiting IRF-1 translation. These findings elucidate a novel mechanism for anti-inflammatory activity of medium-chain fatty acid 10HDA.

Beta interferon regulation of glucose metabolism is PI3K/Akt dependent and important for antiviral activity against coxsackievirus B3

An effective type I interferon (IFN)-mediated immune response requires the rapid expression of antiviral proteins that are necessary to inhibit viral replication and virus spread. We provide evidence that IFN-β regulates metabolic events important for the induction of a rapid antiviral response: IFN-β decreases the phosphorylation of AMP-activated protein kinase (AMPK), coincident with an increase in intracellular ATP. Our studies reveal a biphasic IFN-β-inducible uptake of glucose by cells, mediated by phosphatidylinositol 3-kinase (PI3K)/Akt, and IFN-β-inducible regulation of GLUT4 translocation to the cell surface. Additionally, we provide evidence that IFN-β-regulated glycolytic metabolism is important for the acute induction of an antiviral response during infection with coxsackievirus B3 (CVB3). Last, we demonstrate that the antidiabetic drug metformin enhances the antiviral potency of IFN-β against CVB3 both in vitro and in vivo. Taken together, these findings highlight an important role for IFN-β in modulating glucose metabolism during a virus infection and suggest that the use of metformin in combination with IFN-β during acute virus infection may result in enhanced antiviral responses.

IMPORTANCE

Type I interferons (IFN) are critical effectors of an antiviral response. These studies describe for the first time a role for IFN-β in regulating metabolism--glucose uptake and ATP production--to meet the energy requirements of a robust cellular antiviral response. Our data suggest that IFN-β regulates glucose metabolism mediated by signaling effectors similarly to activation by insulin. Interference with IFN-β-inducible glucose metabolism diminishes the antiviral response, whereas treatment with metformin, a drug that increases insulin sensitivity, enhances the antiviral potency of IFN-β.

Regulation of interferon-dependent mRNA translation of target genes

Interferons (IFNs) are released by cells on exposure to various stimuli, including viruses, double-stranded RNA, and other cytokines and various polypeptides. These IFNs play important physiological and pathophysiological roles in humans. Many clinical studies have established activity for these cytokines in the treatment of several malignancies, viral syndromes, and autoimmune disorders. In this review, the regulatory effects of type I and II IFN receptors on the translation-initiation process mediated by mechanistic target of rapamycin (mTOR) and mitogen-activated protein kinase (MAPK) pathways and the known mechanisms of control of mRNA translation of IFN-stimulated genes are summarized and discussed.

Type I Interferon at the Interface of Antiviral Immunity and Immune Regulation: The Curious Case of HIV-1

Type I interferon (IFN-I) play a critical role in the innate immune response against viral infections. They actively participate in antiviral immunity by inducing molecular mechanisms of viral restriction and by limiting the spread of the infection, but they also orchestrate the initial phases of the adaptive immune response and influence the quality of T cell immunity. During infection with the human immunodeficiency virus type 1 (HIV-1), the production of and response to IFN-I may be severely altered by the lymphotropic nature of the virus. In this review I consider the different aspects of virus sensing, IFN-I production, signalling, and effects on target cells, with a particular focus on the alterations observed following HIV-1 infection.

Inducing autophagy: a comparative phosphoproteomic study of the cellular response to ammonia and rapamycin

Autophagy is a lysosomal-mediated catabolic process, which through degradation of different cytoplasmic components aids in maintaining cellular homeostasis and survival during exposure to extra- or intracellular stresses. Ammonia is a potential toxic and stress-inducing byproduct of glutamine catabolism, which has recently been found to induce autophagy in an MTOR independent way and support cancer cell survival. In this study, quantitative phosphoproteomics was applied to investigate the initial signaling events linking ammonia to the induction of autophagy. The MTOR inhibitor rapamycin was used as a reference treatment to emphasize the differences between an MTOR-dependent and -independent autophagy-induction. By this means 5901 phosphosites were identified of which 626 were treatment-specific regulated and 175 were coregulated. Investigation of the ammonia-specific regulated sites supported that MTOR activity was not affected, but indicated increased MAPK3 activity, regulation of proteins involved in Rho signal transduction, and a novel phosphorylation motif, serine-proline-threonine (SPT), which could be linked to cytoskeleton-associated proteins. MAPK3 could not be identified as the primary driver of ammonia-induced autophagy but instead the data suggested an upregulation of AMPK and the unfolded protein response (UPR), which might link ammonia to autophagy induction. Support of UPR induction was further obtained from the finding of increased protein levels of the ER stress markers DDIT3/CHOP and HSPA5 during ammonia treatment. The large-scale data set presented here comprises extensive high-quality quantitative information on phosphoprotein regulation in response to 2 very different autophagy inducers and should therefore be considered a general resource for the community.

Kinase-substrate enrichment analysis provides insights into the heterogeneity of signaling pathway activation in leukemia cells

Kinases determine the phenotypes of many cancer cells, but the frequency with which individual kinases are activated in primary tumors remains largely unknown. We used a computational approach, termed kinase-substrate enrichment analysis (KSEA), to systematically infer the activation of given kinase pathways from mass spectrometry-based phosphoproteomic analysis of acute myeloid leukemia (AML) cells. Experiments conducted in cell lines validated the approach and, furthermore, revealed that DNA-dependent protein kinase (DNA-PK) was activated as a result of inhibiting the phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) signaling pathway. Application of KSEA to primary AML cells identified PI3K, casein kinases (CKs), cyclin-dependent kinases (CDKs), and p21-activated kinases (PAKs) as the kinase substrate groups most frequently enriched in this cancer type. Substrates phosphorylated by extracellular signal-regulated kinase (ERK) and cell division cycle 7 (CDC7) were enriched in primary AML cells that were resistant to inhibition of PI3K-mTOR signaling, whereas substrates of the kinases Abl, Lck, Src, and CDK1 were increased in abundance in inhibitor-sensitive cells. Modeling based on the abundances of these substrate groups accurately predicted sensitivity to a dual PI3K and mTOR inhibitor in two independent sets of primary AML cells isolated from patients. Thus, our study demonstrates KSEA as an untargeted method for the systematic profiling of kinase pathway activities and for increasing our understanding of diseases caused by the dysregulation of signaling pathways.

Type I interferons induce autophagy in certain human cancer cell lines

Autophagy is an evolutionarily conserved cellular recycling mechanism that occurs at a basal level in all cells. It can be further induced by various stimuli including starvation, hypoxia, and treatment with cytokines such as IFNG/IFNγ and TGFB/TGFβ. Type I IFNs are proteins that induce an antiviral state in cells. They also have antiproliferative, proapoptotic and immunomodulatory activities. We investigated whether type I IFN can also induce autophagy in multiple human cell lines. We found that treatment with IFNA2c/IFNα2c and IFNB/IFNβ induces autophagy by 24 h in Daudi B cells, as indicated by an increase of autophagy markers MAP1LC3-II, ATG12–ATG5 complexes, and a decrease of SQSTM1 expression. An increase of MAP1LC3-II was also detected 48 h post-IFNA2c treatment in HeLa S3, MDA-MB-231, T98G and A549 cell lines. The presence of autophagosomes in selected cell lines exposed to type I IFN was confirmed by electron microscopy analysis. Increased expression of autophagy markers correlated with inhibition of MTORC1 in Daudi cells, as well as inhibition of cancer cell proliferation and changes in cell cycle progression. Concomitant blockade of either MTOR or PI3K-AKT signaling in Daudi and T98G cells treated with IFNA2c increased the level of MAP1LC3-II, indicating that the PI3K-AKT-MTORC1 signaling pathway may modulate IFN-induced autophagy in these cells. Taken together, our findings demonstrated a novel function of type I IFN as an inducer of autophagy in multiple cell lines.

Regulatory effects of programmed cell death 4 (PDCD4) protein in interferon (IFN)-stimulated gene expression and generation of type I IFN responses

The precise mechanisms by which the activation of interferon (IFN) receptors (IFNRs) ultimately controls mRNA translation of specific target genes to induce IFN-dependent biological responses remain ill defined. We provide evidence that IFN-α induces phosphorylation of programmed cell death 4 (PDCD4) protein on Ser67. This IFN-α-dependent phosphorylation is mediated by either the p70 S6 kinase (S6K) or the p90 ribosomal protein S6K (RSK) in a cell-type-specific manner. IFN-dependent phosphorylation of PDCD4 results in downregulation of PDCD4 protein levels as the phosphorylated form of PDCD4 interacts with the ubiquitin ligase β-TRCP (β-transducin repeat-containing protein) and undergoes degradation. This process facilitates IFN-induced eukaryotic translation initiation factor 4A (eIF4A) activity and binding to translation initiation factor eIF4G to promote mRNA translation. Our data establish that PDCD4 degradation ultimately facilitates expression of several ISG protein products that play important roles in the generation of IFN responses, including IFN-stimulated gene 15 (ISG15), p21(WAF1/CIP1), and Schlafen 5 (SLFN5). Moreover, engagement of the RSK/PDCD4 pathway by the type I IFNR is required for the suppressive effects of IFN-α on normal CD34(+) hematopoietic precursors and for antileukemic effects in vitro. Altogether, these findings provide evidence for a unique function of PDCD4 in the type I IFN system and indicate a key regulatory role for this protein in mRNA translation of ISGs and control of IFN responses.

Regulatory effects of mTORC2 complexes in type I IFN signaling and in the generation of IFN responses

IFNs transduce signals by binding to cell surface receptors and activating cellular pathways and regulatory networks that control transcription of IFN-stimulated genes (ISGs) and mRNA translation, leading to generation of protein products that mediate biological responses. Previous studies have shown that type I IFN receptor-engaged pathways downstream of AKT and mammalian target of rapamycin complex (mTORC) 1 play important roles in mRNA translation of ISGs and the generation of IFN responses, but the roles of mTORC2 complexes in IFN signaling are unknown. We provide evidence that mTORC2 complexes control IFN-induced phosphorylation of AKT on serine 473 and their function is ultimately required for IFN-dependent gene transcription via interferon-stimulated response elements. We also demonstrate that such complexes exhibit regulatory effects on other IFN-dependent mammalian target of rapamycin-mediated signaling events, likely via engagement of the AKT/mTORC1 axis, including IFN-induced phosphorylation of S6 kinase and its effector rpS6, as well as phosphorylation of the translational repressor 4E-binding protein 1. We also show that induction of ISG protein expression and the generation of antiviral responses are defective in Rictor and mLST8-KO cells. Together, our data provide evidence for unique functions of mTORC2 complexes in the induction of type I IFN responses and suggest a critical role for mTORC2-mediated signals in IFN signaling.

Immunomodulatory functions of type I interferons

Interferon-α (IFNα) and IFNβ, collectively known as type I IFNs, are the major effector cytokines of the host immune response against viral infections. However, the production of type I IFNs is also induced in response to bacterial ligands of innate immune receptors and/or bacterial infections, indicating a broader physiological role for these cytokines in host defence and homeostasis than was originally assumed. The main focus of this Review is the underappreciated immunomodulatory functions of type I IFNs in health and disease. We discuss their function in the regulation of innate and adaptive immune responses, the response to bacterial ligands, inflammasome activation, intestinal homeostasis and inflammatory and autoimmune diseases.

Dual phosphoproteomics and chemical proteomics analysis of erlotinib and gefitinib interference in acute myeloid leukemia cells

Small molecule inhibitors of protein kinases have emerged as a major class of therapeutic agents for the treatment of hematological malignancies. Both in vitro studies and patient case reports suggest therapeutic potential of the clinical kinase inhibitors erlotinib and gefitinib in acute myeloid leukemia (AML). The drugs' cellular modes of action in AML warrant further investigation as their primary therapeutic target, the epidermal growth factor receptor, is not expressed. We therefore performed SILAC-based quantitative mass spectrometry analyses to a depth of 10,975 distinct phosphorylation sites to characterize the phosphoproteome of KG1 AML cells and its regulation upon erlotinib and gefitinib treatment. Less than 50 site-specific phosphorylations changed significantly, indicating rather specific interference with AML cell signaling. Many drug-induced changes occurred within a network of tyrosine phosphorylated proteins that included Src family kinases (SFKs) and the tyrosine kinases Btk and Syk. We further performed quantitative chemical proteomics in KG1 cell extracts and identified SFKs and Btk as direct cellular targets of both erlotinib and gefitinib. Taken together, our data suggest that cellular perturbation of SFKs and/or Btk translates into rather specific signal transduction inhibition, which in turn contributes to the antileukemic activity of erlotinib and gefitinib in AML.

Antiviral effects of interferon-β are enhanced in the absence of the translational suppressor 4E-BP1 in myocarditis induced by Coxsackievirus B3

BACKGROUND

Viral myocarditis is most frequently associated with infection by Coxsackievirus B3 (CVB3). Interferon (IFN)-β therapy has been studied and could reduce virally induced tissue damage and improve heart function.

METHODS

In the present study we have investigated the role of translational suppression in the context of an IFN-α/β-mediated antiviral immune response to CVB3 infection. Specifically, we examined the effects of IFN-α/β treatment of CVB3-infected mouse embryonic fibroblast cells and splenocytes lacking eukaryotic initiation factor 4E binding protein-1 (4E-BP1), a suppressor of 5'-capped mRNA translation. Extending these in vitro studies, we examined the effects of CVB3 infection and IFN-β treatment in 4E-BP1(-/-) mice.

RESULTS

Our data show that 4E-BP1(-/-) cells are more -sensitive to the antiviral effects of IFN-α4 and IFN-β treatment than 4E-BP1(+/+) cells when infected with CVB3. Similarly, 4E-BP1(-/-) mice are more sensitive to treatment with IFN-β, exhibiting lower viral titres in heart tissue than 4E-BP1(+/+) mice during the course of infection. Additionally, we demonstrate that treatment with IFN-β reduces inflammatory infiltrates into the hearts of infected mice.

CONCLUSIONS

These data identify 4E-BP1 as a novel drug target to augment responsiveness to IFN-β therapy in CVB3-induced myocarditis.

Possible role of phosphoinositide-3-kinase in Mx1 protein translation and antiviral activity of interferon-omega-stimulated HeLa cells

Interferon ω (IFN-ω), a cytokine released during innate immune activation, is well known for promoting direct antiviral responses; however, the possible signal pathways that are initiated by IFN-ω binding to the type I IFN receptors have not been fully studied. Here, we provide evidence that activation of phosphoinositide-3-kinase/protein kinase B (PI3K/Akt) signaling plays a pivotal role in the generation of IFN-ω-mediated biological responses. We found that LY294002 (PI3K inhibitor)-attenuated antiviral activities are induced by IFN-ω treatment. Although such effects of LY294002 are unrelated to regulatory activities on IFN-ω-dependent Mx1 (myxovirus resistance 1) or Mx2 gene transcriptional regulation, translation of Mx1 protein, which was known as a key mediator of cell-autonomous antiviral resistance, was significantly reduced by PI3K inhibition. Further studies showed that PI3K inhibition using LY294002 leads to a decrease in PI3K substrate Akt and mitogen-activated protein kinase extracellular signal-regulated kinase and p38 phosphorylation/activation. In addition, although LY294002 was not able to reduce STAT1 activation, we found that the mammalian target of rapamycin (mTOR)/p70 S6 kinase pathway was significantly attenuated by inhibition of the PI3K/Akt signaling pathway. These results indicate that the PI3K/Akt pathway is a common and central integrator for antiviral responses in IFN-ω signaling via its regulatory effects on mTOR that are required for initiation of mRNA translation of Mx genes.

The kinase mTOR regulates the differentiation of helper T cells through the selective activation of signaling by mTORC1 and mTORC2

The kinase mTOR has emerged as an important regulator of the differentiation of helper T cells. Here we demonstrate that differentiation into the T(H)1 and T(H)17 subsets of helper T cells was selectively regulated by signaling from mTOR complex 1 (mTORC1) that was dependent on the small GTPase Rheb. Rheb-deficient T cells failed to generate T(H)1 and T(H)17 responses in vitro and in vivo and did not induce classical experimental autoimmune encephalomyelitis (EAE). However, they retained their ability to become T(H)2 cells. Alternatively, when mTORC2 signaling was deleted from T cells, they failed to generate T(H)2 cells in vitro and in vivo but preserved their ability to become T(H)1 and T(H)17 cells. Our data identify mechanisms by which two distinct signaling pathways downstream of mTOR regulate helper cell fate in different ways. These findings define a previously unknown paradigm that links T cell differentiation with selective metabolic signaling pathways.

Role of interferon {alpha} (IFN{alpha})-inducible Schlafen-5 in regulation of anchorage-independent growth and invasion of malignant melanoma cells

IFNα exerts potent inhibitory activities against malignant melanoma cells in vitro and in vivo, but the mechanisms by which it generates its antitumor effects remain unknown. We examined the effects of interferon α (IFNα) on the expression of human members of the Schlafen (SLFN) family of genes, a group of cell cycle regulators that mediate growth-inhibitory responses. Using quantitative RT-real time PCR, we found detectable basal expression of all the different human SLFN genes examined (SLFN5, SLFN11, SLFN12, SLFN13, and SLFN14), in malignant melanoma cells and primary normal human melanocytes, but SLFN5 basal expression was suppressed in all analyzed melanoma cell lines. Treatment of melanoma cells with IFNα resulted in induction of expression of SLFN5 in malignant cells, suggesting a potential involvement of this gene in the antitumor effects of IFNα. Importantly, stable knockdown of SLFN5 in malignant melanoma cells resulted in increased anchorage-independent growth, as evidenced by enhanced colony formation in soft agar assays. Moreover, SLFN5 knockdown also resulted in increased invasion in three-dimensional collagen, suggesting a dual role for SLFN5 in the regulation of invasion and anchorage-independent growth of melanoma cells. Altogether, our findings suggest an important role for the SLFN family of proteins in the generation of the anti-melanoma effects of IFNα and for the first time directly implicate a member of the human SLFN family in the regulation of cell invasion.

The mammalian target of rapamycin: linking T cell differentiation, function, and metabolism

In the two-signal model of T cell activation, the outcome of antigen recognition is determined by the integration of multiple cues in the immune microenvironment. mTOR is an evolutionarily conserved PI3-kinase family member that plays a central role in integrating environmental cues in the form of amino acids, energy, and growth factors. Recently, an increasingly important role for mTOR in directing T cell activation and differentiation has become apparent. Here we review recent findings demonstrating the ability of mTOR to interpret signals in the immune microenvironment and program the generation of CD4(+) effector versus regulatory T cells, the generation of CD8(+) effector versus memory cells, T cell trafficking, and T cell activation versus anergy. The key theme to emerge from these studies is that the central role of mTOR provides a direct link between T cell metabolism and function.

Interferons modulate mitogen-induced protein synthesis in airway smooth muscle

Severe asthma is characterized by increased airway smooth muscle (ASM) mass due, in part, to ASM cell growth and contractile protein expression associated with increased protein synthesis. Little is known regarding the combined effects of mitogens and interferons on ASM cytosolic protein synthesis. We demonstrate that human ASM mitogens including PDGF, EGF, and thrombin stimulate protein synthesis. Surprisingly, pleiotropic cytokines IFN-beta and IFN-gamma, which inhibit ASM proliferation, also increased cytosolic protein content in ASM cells. Thus IFN-beta alone significantly increased protein synthesis by 1.62 +/- 0.09-fold that was further enhanced by EGF to 2.52 +/- 0.17-fold. IFN-gamma alone also stimulated protein synthesis by 1.91 +/- 0.15-fold; treatment of cells with PDGF, EGF, and thrombin in the presence of IFN-gamma stimulated protein synthesis by 2.24 +/- 0.3-, 1.25 +/- 0.17-, and 2.67 +/- 0.34-fold, respectively, compared with growth factors alone. The mammalian target of rapamycin (mTOR)/S6 kinase 1 (S6K1) inhibition with rapamycin inhibited IFN- and EGF-induced protein synthesis, suggesting that IFN-induced protein synthesis is modulated by mTOR/S6K1 activation. Furthermore, overexpression of tumor suppressor protein tuberous sclerosis complex 2 (TSC2), which is an upstream negative regulator of mTOR/S6K1 signaling, also inhibited mitogen-induced protein synthesis in ASM cells. IFN-beta and IFN-gamma stimulated miR143/145 microRNA expression and increased SM alpha-actin accumulation but had little effect on ASM cell size. In contrast, EGF increased ASM cell size but had little effect on miR143/145 expression. Our data demonstrate that both IFNs and mitogens stimulate protein synthesis but have differential effects on cell size and contractile protein expression and suggest that combined effects of IFNs and mitogens may contribute to ASM cell growth, contractile protein expression, and ASM remodeling in asthma.

Interferon-gamma regulates intestinal epithelial homeostasis through converging beta-catenin signaling pathways

Inflammatory cytokines have been proposed to regulate epithelial homeostasis during intestinal inflammation. We report here that interferon-gamma (IFN-gamma) regulates the crucial homeostatic functions of cell proliferation and apoptosis through serine-threonine protein kinase AKT-beta-catenin and Wingless-Int (Wnt)-beta-catenin signaling pathways. Short-term exposure of intestinal epithelial cells to IFN-gamma resulted in activation of beta-catenin through AKT, followed by induction of the secreted Wnt inhibitor Dkk1. Consequently, we observed an increase in Dkk1-mediated apoptosis upon extended IFN-gamma treatment and reduced proliferation through depletion of the Wnt coreceptor LRP6. These effects were enhanced by tumor necrosis factor-alpha (TNF-alpha), suggesting synergism between the two cytokines. Consistent with these results, colitis in vivo was associated with decreased beta-catenin-T cell factor (TCF) signaling, loss of plasma membrane-associated LRP6, and reduced epithelial cell proliferation. Proliferation was partially restored in IFN-gamma-deficient mice. Thus, we propose that IFN-gamma regulates intestinal epithelial homeostasis by sequential regulation of converging beta-catenin signaling pathways.

Mutations in CHMP2B in lower motor neuron predominant amyotrophic lateral sclerosis (ALS)

BACKGROUND

Amyotrophic lateral sclerosis (ALS), a common late-onset neurodegenerative disease, is associated with fronto-temporal dementia (FTD) in 3-10% of patients. A mutation in CHMP2B was recently identified in a Danish pedigree with autosomal dominant FTD. Subsequently, two unrelated patients with familial ALS, one of whom also showed features of FTD, were shown to carry missense mutations in CHMP2B. The initial aim of this study was to determine whether mutations in CHMP2B contribute more broadly to ALS pathogenesis.

METHODOLOGY/PRINCIPAL FINDINGS

Sequencing of CHMP2B in 433 ALS cases from the North of England identified 4 cases carrying 3 missense mutations, including one novel mutation, p.Thr104Asn, none of which were present in 500 neurologically normal controls. Analysis of clinical and neuropathological data of these 4 cases showed a phenotype consistent with the lower motor neuron predominant (progressive muscular atrophy (PMA)) variant of ALS. Only one had a recognised family history of ALS and none had clinically apparent dementia. Microarray analysis of motor neurons from CHMP2B cases, compared to controls, showed a distinct gene expression signature with significant differential expression predicting disassembly of cell structure; increased calcium concentration in the ER lumen; decrease in the availability of ATP; down-regulation of the classical and p38 MAPK signalling pathways, reduction in autophagy initiation and a global repression of translation. Transfection of mutant CHMP2B into HEK-293 and COS-7 cells resulted in the formation of large cytoplasmic vacuoles, aberrant lysosomal localisation demonstrated by CD63 staining and impairment of autophagy indicated by increased levels of LC3-II protein. These changes were absent in control cells transfected with wild-type CHMP2B.

CONCLUSIONS/SIGNIFICANCE

We conclude that in a population drawn from North of England pathogenic CHMP2B mutations are found in approximately 1% of cases of ALS and 10% of those with lower motor neuron predominant ALS. We provide a body of evidence indicating the likely pathogenicity of the reported gene alterations. However, absolute confirmation of pathogenicity requires further evidence, including documentation of familial transmission in ALS pedigrees which might be most fruitfully explored in cases with a LMN predominant phenotype.

Growth suppressive cytokines and the AKT/mTOR pathway

The mTOR signaling pathway plays a very important role in the transmission of signals for initiation of mRNA translation and protein expression in mammalian cells. mTOR activates various downstream effectors to promote initiation of cap-dependent mRNA translation and mediate pro-mitogenic and pro-survival signals. Recent evidence has implicated effectors of this signaling cascade in mRNA translation for interferon stimulated genes (ISGs). In addition, it was recently shown that AKT/mTOR-mediated signals play important roles in the generation of IFN-dependent antiviral and growth inhibitory responses, suggesting that mTOR and its effectors can mediate diverse biological responses, depending on the cellular context and the triggering stimuli. In this review, the regulatory effects of various growth suppressive cytokines on the mTOR pathway are summarized and the emerging new functions of mTOR are discussed.

Role of Schlafen 2 (SLFN2) in the generation of interferon alpha-induced growth inhibitory responses

The precise STAT-regulated gene targets that inhibit cell growth and generate the antitumor effects of Type I interferons (IFNs) remain unknown. We provide evidence that Type I IFNs regulate expression of Schlafens (SLFNs), a group of genes involved in the control of cell cycle progression and growth inhibitory responses. Using cells with targeted disruption of different STAT proteins and/or the p38 MAP kinase, we demonstrate that the IFN-dependent expression of distinct Schlafen genes is differentially regulated by STAT complexes and the p38 MAP kinase pathway. We also provide evidence for a key functional role of a member of the SLFN family, SLFN2, in the induction of the growth-suppressive effects of IFNs. This is shown in studies demonstrating that knockdown of SLFN2 enhances hematopoietic progenitor colony formation and reverses the growth-suppressive effects of IFNalpha on normal hematopoietic progenitors. Importantly, NIH3T3 or L929 cells with stable knockdown of SLFN2 form more colonies in soft agar, implicating this protein in the regulation of anchorage-independent growth. Altogether, our data implicate SLFN2 as a negative regulator of the metastatic and growth potential of malignant cells and strongly suggest a role for the SLFN family of proteins in the generation of the antiproliferative effects of Type I IFNs.

Type I interferon (IFN)-dependent activation of Mnk1 and its role in the generation of growth inhibitory responses

We provide evidence for the existence of an IFN-regulated cellular pathway involving the mitogen-activated protein kinase (MAPK)-integrating kinase (Mnk) 1. Our data demonstrate that type I (alpha, beta) IFNs induce phosphorylation/activation of Mnk1, which, in turn, regulates phosphorylation of the eukaryotic initiation factor 4E (eIF4E) on Ser-209. Such Mnk activation depends on upstream engagement of Jak1, and requires downstream activation of the Mek/Erk MAPK pathway. In studies using double Mnk1-/-Mnk2-/- knockout mouse embryonic fibroblasts (MEFs), we found that engagement of Mnk kinases is essential for mRNA translation of the Isg15 and Isg54 genes, suggesting an important role for this pathway in mRNA translation of IFN-stimulated genes (ISGs). Importantly, our data demonstrate that pharmacological inhibition of Mnk kinases or siRNA-mediated knockdown of Mnk1 and Mnk2 results in partial reversal of the suppressive effects of IFNalpha on normal and leukemic hematopoietic progenitors, establishing a key role for this pathway in the generation of the growth inhibitory effects of type I IFNs. Together, our findings establish that the Mnk/eIF4E kinase pathway is activated in an IFN-inducible manner and plays important roles in mRNA translation for ISGs and generation of IFN-inducible anti-proliferative responses.

Influence of signal transducer and activator of transcription-1 signaling on thyroid morphology and function

Interferon (IFN)-gamma has been involved in the pathogenesis of Hashimoto thyroiditis. It is a cytokine released by infiltrating mononuclear cells that mediates its actions mainly through signal transducer and activator of transcription-1 (STAT1) but also through other transcription factors. To dissect the effect of IFN gamma on thyroid morphology and function, we crossed transgenic mice that express IFN gamma specifically in the thyroid gland to mice deficient in STAT1. Lack of STAT1 ameliorated the abnormal thyroid morphology and the primary hypothyroidism typical of IFN gamma transgenic mice but not the suppressed iodine accumulation. Interestingly, lack of STAT1 alone decreased iodine accumulation, seemingly through expression of TGFbeta. These results indicate that STAT1 is required to mediate some but not all of the phenotypic changes induced by IFN gamma and that it also regulates iodine accumulation via TGFbeta signaling.