The helicase HAGE prevents interferon-a-induced PML expression in ABCB5+ malignant melanoma-initiating cells by promoting the expression of SOCS1

The tumour suppressor PML (promyelocytic leukaemia protein) regulates several cellular pathways involving cell growth, apoptosis, differentiation and senescence. PML also has an important role in the regulation of stem cell proliferation and differentiation. Here, we show the involvement of the helicase HAGE in the transcriptional repression of PML expression in ABCB5 + malignant melanoma-initiating cells (ABCB5 + MMICs), a population of cancer stem cells which are responsible for melanoma growth, progression and resistance to drug-based therapy. HAGE prevents PML gene expression by inhibiting the activation of the JAK-STAT (janus kinase-signal transducers and activators of transcription) pathway in a mechanism which implicates the suppressor of cytokine signalling 1 (SOCS1). Knockdown of HAGE led to a significant decrease in SOCS1 protein expression, activation of the JAK-STAT signalling cascade and a consequent increase of PML expression. To confirm that the reduction in SOCS1 expression was dependent on the HAGE helicase activity, we showed that SOCS1, effectively silenced by small interfering RNA, could be rescued by re-introduction of HAGE into cells lacking HAGE. Furthermore, we provide a mechanism by which HAGE promotes SOCS1 mRNA unwinding and protein expression in vitro

TYK2 Kinase Activity Is Required for Functional Type I Interferon Responses In Vivo

Tyrosine kinase 2 (TYK2) is a member of the Janus kinase (JAK) family and is involved in cytokine signalling. In vitro analyses suggest that TYK2 also has kinase-independent, i.e., non-canonical, functions. We have generated gene-targeted mice harbouring a mutation in the ATP-binding pocket of the kinase domain. The Tyk2 kinase-inactive (Tyk2K923E) mice are viable and show no gross abnormalities. We show that kinase-active TYK2 is required for full-fledged type I interferon- (IFN) induced activation of the transcription factors STAT1-4 and for the in vivo antiviral defence against viruses primarily controlled through type I IFN actions. In addition, TYK2 kinase activity was found to be required for the protein’s stability. An inhibitory function was only observed upon over-expression of TYK2K923E in vitro. Tyk2K923E mice represent the first model for studying the kinase-independent function of a JAK in vivo and for assessing the consequences of side effects of JAK inhibitors

Viruses exacerbating chronic pulmonary disease: the role of immune modulation

Chronic pulmonary diseases are a major cause of morbidity and mortality and their impact is expected to increase in the future. Respiratory viruses are the most common cause of acute respiratory infections and it is increasingly recognized that respiratory viruses are a major cause of acute exacerbations of chronic pulmonary diseases such as asthma, chronic obstructive pulmonary disease and cystic fibrosis. There is now increasing evidence that the host response to virus infection is dysregulated in these diseases and a better understanding of the mechanisms of abnormal immune responses has the potential to lead to the development of new therapies for virus-induced exacerbations. The aim of this article is to review the current knowledge regarding the role of viruses and immune modulation in chronic pulmonary diseases and discuss avenues for future research and therapeutic implications

Analysis of the human monocyte-derived macrophage transcriptome and response to lipopolysaccharide provides new insights into genetic aetiology of inflammatory bowel disease

The FANTOM5 consortium utilised cap analysis of gene expression (CAGE) to provide an unprecedented insight into transcriptional regulation in human cells and tissues. In the current study, we have used CAGE-based transcriptional profiling on an extended dense time course of the response of human monocyte-derived macrophages grown in macrophage colony-stimulating factor (CSF1) to bacterial lipopolysaccharide (LPS). We propose that this system provides a model for the differentiation and adaptation of monocytes entering the intestinal lamina propria. The response to LPS is shown to be a cascade of successive waves of transient gene expression extending over at least 48 hours, with hundreds of positive and negative regulatory loops. Promoter analysis using motif activity response analysis (MARA) identified some of the transcription factors likely to be responsible for the temporal profile of transcriptional activation. Each LPS-inducible locus was associated with multiple inducible enhancers, and in each case, transient eRNA transcription at multiple sites detected by CAGE preceded the appearance of promoter-associated transcripts. LPS-inducible long non-coding RNAs were commonly associated with clusters of inducible enhancers. We used these data to re-examine the hundreds of loci associated with susceptibility to inflammatory bowel disease (IBD) in genome-wide association studies. Loci associated with IBD were strongly and specifically (relative to rheumatoid arthritis and unrelated traits) enriched for promoters that were regulated in monocyte differentiation or activation. Amongst previously-identified IBD susceptibility loci, the vast majority contained at least one promoter that was regulated in CSF1-dependent monocyte-macrophage transitions and/or in response to LPS. On this basis, we concluded that IBD loci are strongly-enriched for monocyte-specific genes, and identified at least 134 additional candidate genes associated with IBD susceptibility from reanalysis of published GWA studies. We propose that dysregulation of monocyte adaptation to the environment of the gastrointestinal mucosa is the key process leading to inflammatory bowel disease

Autoimmune aspects of psoriasis: Heritability and autoantigens

Chronic immune-mediated disorders (IMDs) constitute a major health burden. Understanding IMD pathogenesis is facing two major constraints: Missing heritability explaining familial clustering, and missing autoantigens. Pinpointing IMD risk genes and autoimmune targets, however, is of fundamental importance for developing novel causal therapies. The strongest association of all IMDs is seen with human leukocyte antigen (HLA) alleles. Using psoriasis as an IMD model this article reviews the pathogenic role HLA molecules may have within the polygenic predisposition of IMDs. It concludes that disease-associated HLA alleles account for both missing heritability and autoimmune mechanisms by facilitating tissue-specific autoimmune responses through autoantigen presentation. (C) 2017 The Author. Published by Elsevier B.V

Characterisation of suppressor of cytokine signaling 1 regulation of type I interferon signaling

Type I Interferons (IFNs) are critical players in host innate and adaptive immunity. IFN signaling is tightly controlled to ensure an appropriate immune response is generated, as an imbalance could result in uncontrolled inflammation or inadequate responses to infection. It is therefore important to understand the signaling events activated in the cell following type I IFN stimulation and how signaling is regulated. SOCS1 is a negative regulator of type I IFN signaling, acting in a negative feedback loop. This thesis details the mechanism of SOCS1 regulation of type I IFN signaling as well as the consequences of this regulation in terms of its effect on IFNα induced STAT activation and the resultant transcriptional response. Results in this thesis demonstrate that SOCS1 inhibits type I IFN signaling through an interaction with the type I IFN receptor (IFNAR1) associated kinase, TYK2. SOCS1 associates via its SH2 domain with conserved phospho-tyrosines 1054 and 1055 of TYK2 as well with the kinase inhibitor region (KIR). TYK2 is preferentially Lys-63 polyubiquitinated and this activation reaction is inhibited by SOCS1. The consequent effect of SOCS1 inhibition of TYK2 not only results in a reduced IFN response due to inhibition of TYK2 kinase mediated STAT signaling, but also negatively impacts IFNAR1 surface expression which is stabilised by TYK2. The STAT family of transcription factors are major mediators of the type I IFN response. This thesis demonstrates STAT activation by the type I IFNs occurs in a cell-type specific manner. STAT1 is up-regulated by type I IFN in a broad range of immune cell types including thymic and peripheral T-cells, B-cells and macrphages whereas activation of STAT3 and STAT5 is more confined to the thymic T-cells. Type I IFN stimulation of thymic cells results in rapid phosphorylation of STAT1, STAT3 and STAT5 and the resultant transcriptional response results in the up-regulation of an array of genes involved in innate defence. The promoter regions of these genes are enriched in ISGF3, STAT1, STAT3 and STAT5 binding elements. Results of this thesis demonstrate that the downstream consequence of SOCS1 action is to suppress IFN induced STAT activation and subsequent gene induction. We found SOCS1 selectively regulates STAT phosphorylation in response to IFNα. The activation profile of STAT1 and STAT3 is altered by SOCS1, whereas STAT5 is independent of this regulation. Using microarray expression profiling, we identified subsets of IFN stimulated genes regulated by SOCS1. Promoter analysis of these gene sets identifies transcription factor enrichment of numerous ISGF3, STAT1 and STAT3 binding sites but not STAT5. These results support a model whereby SOCS1 negative regulation of type I IFN signaling selectively modulates the activation profile of STAT1 and STAT3 and consequent gene induction. These studies have mapped specific pathways of IFN regulation from the receptor component to transcription factor activation and interferon regulated gene induction. I demonstrate that SOCS1 selectively interacts with the IFNAR1 associated kinase, TYK2 and regulates the signaling of a subset of IFN activated STATs and IFN/STAT regulated genes. These findings therefore enhance our understanding of type I IFN signaling and its regulation by SOCS1 and provide the foundation for future therapies to select for specific type I IFN signaling pathways

Characterisation of suppressor of cytokine signaling 1 regulation of type I interferon signaling

Type I Interferons (IFNs) are critical players in host innate and adaptive immunity. IFN signaling is tightly controlled to ensure an appropriate immune response is generated, as an imbalance could result in uncontrolled inflammation or inadequate responses to infection. It is therefore important to understand the signaling events activated in the cell following type I IFN stimulation and how signaling is regulated. SOCS1 is a negative regulator of type I IFN signaling, acting in a negative feedback loop. This thesis details the mechanism of SOCS1 regulation of type I IFN signaling as well as the consequences of this regulation in terms of its effect on IFNα induced STAT activation and the resultant transcriptional response. Results in this thesis demonstrate that SOCS1 inhibits type I IFN signaling through an interaction with the type I IFN receptor (IFNAR1) associated kinase, TYK2. SOCS1 associates via its SH2 domain with conserved phospho-tyrosines 1054 and 1055 of TYK2 as well with the kinase inhibitor region (KIR). TYK2 is preferentially Lys-63 polyubiquitinated and this activation reaction is inhibited by SOCS1. The consequent effect of SOCS1 inhibition of TYK2 not only results in a reduced IFN response due to inhibition of TYK2 kinase mediated STAT signaling, but also negatively impacts IFNAR1 surface expression which is stabilised by TYK2. The STAT family of transcription factors are major mediators of the type I IFN response. This thesis demonstrates STAT activation by the type I IFNs occurs in a cell-type specific manner. STAT1 is up-regulated by type I IFN in a broad range of immune cell types including thymic and peripheral T-cells, B-cells and macrphages whereas activation of STAT3 and STAT5 is more confined to the thymic T-cells. Type I IFN stimulation of thymic cells results in rapid phosphorylation of STAT1, STAT3 and STAT5 and the resultant transcriptional response results in the up-regulation of an array of genes involved in innate defence. The promoter regions of these genes are enriched in ISGF3, STAT1, STAT3 and STAT5 binding elements. Results of this thesis demonstrate that the downstream consequence of SOCS1 action is to suppress IFN induced STAT activation and subsequent gene induction. We found SOCS1 selectively regulates STAT phosphorylation in response to IFNα. The activation profile of STAT1 and STAT3 is altered by SOCS1, whereas STAT5 is independent of this regulation. Using microarray expression profiling, we identified subsets of IFN stimulated genes regulated by SOCS1. Promoter analysis of these gene sets identifies transcription factor enrichment of numerous ISGF3, STAT1 and STAT3 binding sites but not STAT5. These results support a model whereby SOCS1 negative regulation of type I IFN signaling selectively modulates the activation profile of STAT1 and STAT3 and consequent gene induction. These studies have mapped specific pathways of IFN regulation from the receptor component to transcription factor activation and interferon regulated gene induction. I demonstrate that SOCS1 selectively interacts with the IFNAR1 associated kinase, TYK2 and regulates the signaling of a subset of IFN activated STATs and IFN/STAT regulated genes. These findings therefore enhance our understanding of type I IFN signaling and its regulation by SOCS1 and provide the foundation for future therapies to select for specific type I IFN signaling pathways

Suppressor of cytokine signaling (SOCS) 1 inhibits type I interferon (IFN) signaling via the interferon alpha receptor (IFNAR1)-associated tyrosine kinase Tyk2

Type I IFNs are critical players in host innate and adaptive immunity. IFN signaling is tightly controlled to ensure appropriate immune responses as imbalance could result in uncontrolled inflammation or inadequate responses to infection. It is therefore important to understand how type I IFN signaling is regulated. Here we have investigated the mechanism by which suppressor of cytokine signaling 1 (SOCS1) inhibits type I IFN signaling. We have found that SOCS1 inhibits type I IFN signaling not via a direct interaction with the IFN ? receptor 1 (IFNAR1) receptor component but through an interaction with the IFNAR1-associated kinase Tyk2. We have characterized the residues/regions involved in the interaction between SOCS1 and Tyk2 and found that SOCS1 associates via its SH2 domain with conserved phosphotyrosines 1054 and 1055 of Tyk2. The kinase inhibitory region of SOCS1 is also essential for its interaction with Tyk2 and inhibition of IFN signaling. We also found that Tyk2 is preferentially Lys-63 polyubiquitinated and that this activation reaction is inhibited by SOCS1. The consequent effect of SOCS1 inhibition of Tyk2 not only results in a reduced IFN response because of inhibition of Tyk2 kinase-mediated STAT signaling but also negatively impacts IFNAR1 surface expression, which is stabilized by Tyk2