Dataset Information

Threonine Phosphorylation of STAT1 Restricts Interferon Signaling and Promotes Innate Inflammatory Responses

ABSTRACT: Since its discovery over three decades ago, signal transducer and activator of transcription 1 (STAT1) has been extensively studied as a central mediator for interferons (IFNs) signaling and antiviral defense. Here, using genetic and biochemical assays, we unveil Thr748 as a conserved IFN-independent phosphorylation switch in Stat1, which restricts IFN signaling and promotes innate inflammatory responses following the recognition of the bacterial-derived toxin lipopolysaccharide (LPS). Genetically-engineered mice expressing phospho-deficient threonine748–to-alanine (T748A) mutant Stat1 are resistant to LPS–induced lethality. Of note, T748A mice exhibited undisturbed IFN signaling, as well as total expression of Stat1. Further, the T748A point-mutation of Stat1 recapitulates the safeguard effect of the genetic ablation of Stat1 following LPS-induced lethality, indicating that the Thr748 phosphorylation contributes inflammatory functionalities of Stat1. Mechanistically, LPS-induced Toll-like receptor 4 endocytosis activates a cell-intrinsic IκB kinase (IKK)–mediated Thr748 phosphorylation of Stat1, which promotes macrophages inflammatory response while restricting the IFN and anti-inflammatory responses. Depletion of macrophages restores the sensitivity of the T748A mice to LPS-induced lethality. Together, our study indicates a phosphorylation-dependent functional dichotomy of Stat1 in innate immune responses: IFN phospho-tyrosine dependent, and inflammatory phospho-threonine dependent. Better understanding of the Thr748 phosphorylation of Stat1 may uncover novel pharmacologically targetable molecules and offer better treatment modalities for sepsis, a disease that claims millions of lives annually.

ORGANISM(S): Mus musculus

PROVIDER: GSE261824 | GEO | 2024/03/18

REPOSITORIES: GEO

ACCESS DATA

Similar Datasets

Project description:Interferon (IFN)γ and interleukin (IL)-4 are central regulators of T helper 1 (Th1) and T helper 2 (Th2) immune responses, respectively. Both cytokines have a major impact on macrophage phenotypes: IFNγ–priming and subsequent TLR4 activation induces so called classically activated macrophages that are characterized by pronounced pro-inflammatory responses, whereas IL-4–treated macrophages, commonly called alternatively activated, are known to develop enhanced capacity for endocytosis, antigen presentation, and tissue repair and are generally considered anti-inflammatory. Considering IL-4 as priming rather than activating stimulus, we now compared the TLR4–dependent global gene activation program in IFNγ– versus IL-4–pretreated mouse macrophages, which has rarely been studied so far. Although both cytokines frequently induced opposing effects on gene transcription, the subsequent activation of bone marrow-derived macrophages by lipopolysaccharide (LPS) produced a strong, priming dependent pro-inflammatory response in both macrophage types. For example, the production of key pro-inflammatory cytokines IL-6 and IL-12 was significantly higher in IL-4– versus IFNγ–primed macrophages and several cytokine genes, including Il19, Ccl17, Ccl22, Ccl24 and Cxcl5, were preferentially induced in alternatively primed and LPS activated mouse macrophages. In a subset of genes, including IL12a, IFNγ priming was actually found to suppress LPS–induced gene expression in a Stat1–dependent manner. Our data suggest that IL-4–priming is not per se anti-inflammatory but generates a macrophage that is “tissue protective” but still capable of mounting a strong inflammatory response after TLR4–dependent activation. Keywords: Gene expression profiling Gene expression was investigated in mouse bone marrow-derived macrophages (BMM). On day 7, BMM were stimulated with either IL-4 or IFNγ overnight (18h in total). LPS treatment was performed in primed and unprimed macrophages 4 h prior to harvesting. At least three independent experiments were performed for each condition.

Project description:Gene regulation by cytokine-activated STAT transcription factors requires serine phosphorylation within the transactivation domain (TAD). STAT1 and STAT3 TAD phosphorylation was reported to occur upon promoter binding by an unknown kinase. Here we show that the Mediator CDK8 module phosphorylates S727 of the STAT1 TAD in the interferon (IFN) signaling pathway as well as the TADs of other STATs. Microarray analysis reveals that CDK8-mediated STAT1 TAD phosphorylation positively or negatively regulates over 40% of IFN-gamma-responsive genes, and RNA polymerase II occupancy correlates with gene expression changes. This selective regulation occurs despite CDK8 occupancy and STAT1 S727 phosphorylation at both S727 phosphorylation-dependent and -independent IFN-gamma target genes. Independently of its role as STAT1 S727 kinase CDK8 acts as a positive regulator of IFN-gamma responses. These data reveal a dual input of CDK8 in STAT1-controlled transcription and propose a key role for CDK8 in TAD phosphorylation of other STATs during cytokine responses. STAT1 WT and STAT1 S727A mouse fibroblasts were treated with siRNA to CDK8 (siCdk8 smart pool, On Target Plus, Dharmacon) and control siRNA (siCtrl) and stimulated with IFN-gamma for 4 h or left untreated. Total RNA from three independent experiments for each treatment and each genotype was isolated from cells using Trizol reagent (Invitrogen) following the manufactures protocol and used for expression analysis using Agilent Whole Mouse Genome Microarrays, 8x60K. Standard protocols for labeling and hybridization were followed. In brief, fluorescent cRNA was generated using Low Input Quick Amp Labeling Kit (Agilent). The amplified cyanine 3-labeled cRNA samples were then purified using SV Total RNA Isolation System (Promega) and hybridized to microarray slides. Microarray slides were washed and scanned with an Agilent Scanner. Note: The outlier array #10 [SA.CDK.gamma.R3] was removed from subsequent analysis and its processed data was not provided. However, its raw data file has been linked as a supplementary file at the foot of the Series record.

Project description:Human cytomegalovirus (hCMV) is a highly prevalent pathogen that, upon primary infection, establishes life-long persistence in all infected individuals. Acute hCMV infections cause a variety of diseases in humans with developmental or acquired immune deficits. In addition, persistent hCMV infection may contribute to various chronic disease conditions even in immunologically normal people. The pathogenesis of hCMV disease has been frequently linked to inflammatory host immune responses triggered by virus-infected cells. Moreover, hCMV infection activates numerous host genes many of which encode pro-inflammatory proteins. However, little is known about the relative contributions of individual viral gene products to these changes in cellular transcription. We systematically analyzed the effects of the hCMV 72-kDa immediate-early 1 (IE1) protein, a major transcriptional activator and antagonist of type I interferon (IFN) signaling, on the human transcriptome. Following expression under conditions closely mimicking the situation during productive infection, IE1 elicits a global type II IFN-like host cell response. This response is dominated by the selective up-regulation of immune stimulatory genes normally controlled by IFN-gamma and includes the synthesis and secretion of pro-inflammatory chemokines. IE1-mediated induction of IFN-stimulated genes strictly depends on tyrosine-phosphorylated signal transducer and activator of transcription 1 (STAT1) and correlates with the nuclear accumulation and sequence-specific binding of STAT1 to IFN-gamma-responsive promoters. However, neither synthesis nor secretion of IFN-gamma or other IFNs seems to be required for the IE1-dependent effects on cellular gene expression. Our results demonstrate that a single hCMV protein can trigger a pro-inflammatory host transcriptional response via an unexpected STAT1-dependent but IFN-independent mechanism and identify IE1 as a candidate determinant of hCMV pathogenicity. We used a total of 18 microarrays for analyzing triplicate samples each of IE1-negative control fibroblasts (TetR cells) without induction (3 arrays), fibroblasts containing inducible IE1 (TetR-IE1 cells) without induction (3 arrays), TetR cells induced for 24 h (3 arrays), TetR-IE1 cells induced for 24 h (3 arrays), TetR cells induced for 72 h (3 arrays), and TetR-IE1 cells induced for 72 h (3 arrays)

Dataset Information

Threonine Phosphorylation of STAT1 Restricts Interferon Signaling and Promotes Innate Inflammatory Responses

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure