Project description:Activation of mTORC1 is crutial for tumorigenesis. Here we identify ZBTB5 as an evolutionarily arisen regulator to translate inflammatory signals to activate mTORC1 pathway in the tumor microenvironment. Mechanistically, inflammatory cytokine TNFα promotes phosphorylation of ZBTB5-S127 confering ZBTB5 as an adaptor to recruit the E3 ubiquitin ligase Cullin3 to activate mTORC1 signaling and promote tumorigenesis. Thus, disrupting inflammation-induced mTORC1 activity represents a promising therapeutic vulnerability of tumor.
Project description:All cells and organisms exhibit stress-coping mechanisms to ensure survival. Cytoplasmic protein-RNA assemblies termed stress granules are increasingly recognized to promote cellular survival under stress. Thus, they might represent tumor vulnerabilities that are currently poorly explored. The translation-inhibitory eIF2α kinases are established as main drivers of stress granule assembly. Using a systems approach, we identify the translation enhancers PI3K and MAPK/p38 as pro-stress-granule-kinases. They act through the metabolic master regulator mammalian target of rapamycin complex 1 (mTORC1) to promote stress granule assembly. When highly active, PI3K is the main driver of stress granules; however, the impact of p38 becomes apparent as PI3K activity declines. PI3K and p38 thus act in a hierarchical manner to drive mTORC1 activity and stress granule assembly. Of note, this signaling hierarchy is also present in human breast cancer tissue. Importantly, only the recognition of the PI3K-p38 hierarchy under stress enabled the discovery of p38’s role in stress granule formation. In summary, we assign a new pro-survival function to the key oncogenic kinases PI3K and p38, as they hierarchically promote stress granule formation.
Project description:M1 macrophages induce protective immunity against infection, but also contribute to metabolic and inflammatory diseases. Here we show that he E3 ubiquitin ligase, MDM2, promotes the glycolytic and inflammatory activities of M1 macrophage by increasing the production of IL-1β, MCP-1 and nitric oxide (NO). Mechanistically, MDM2 triggers the ubiquitination and degradation of E3 ligase, SPSB2, to stabilize iNOS and increases production of NO, which s-nitrosylates and activates HIF-1α for triggering the glycolytic and pro-inflammatory programs in M1 macrophages. Myeloid-specific haplo-deletion of MDM2 in mice not only blunts LPS-induced endotoxemia and NO production, but also alleviates obesity-induced adipose tissue-resident macrophage inflammation. By contrast, MDM2 haplodeletion induces higher mortality, tissue damage and bacterial burden, and also suppresses M1 macrophage response, in the cecal ligation and puncture-induced sepsis mouse model. Our findings thus identify MDM2 as an activator of glycolytic and inflammatory responses in M1 macrophages by connecting the iNOS-NO and HIF-1α pathways.
Project description:All cells and organisms exhibit stress-coping mechanisms toensure survival. Cytoplasmic protein-RNA assemblies termedstress granules are increasingly recognized to promote cellularsurvival under stress. Thus, they might represent tumor vul-nerabilities that are currently poorly explored. The translation-inhibitory eIF2αkinases are established as main drivers ofstress granule assembly. Using a systems approach, we identifythe translation enhancers PI3K and MAPK/p38 as pro-stress-granule-kinases. They act through the metabolic master regu-lator mammalian target of rapamycin complex 1 (mTORC1) topromote stress granule assembly. When highly active, PI3K is themain driver of stress granules; however, the impact of p38becomes apparent as PI3K activity declines. PI3K and p38 thusact in a hierarchical manner to drive mTORC1 activity and stressgranule assembly. Of note, this signaling hierarchy is also presentin human breast cancer tissue. Importantly, only the recognition ofthe PI3K-p38 hierarchy under stress enabled the discovery of p38’srole in stress granule formation. In summary, we assign a new pro-survival function to the key oncogenic kinases PI3K and p38, as theyhierarchically promote stress granule formation
Project description: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.
Project description:The mitogen-activated protein kinase (MAPK) p38 pathway is reported to regulate macrophage responses to lipopolysaccharide (LPS) at least partly via the phosphorylation of the mRNA-destabilizing factor tristetraprolin (TTP). LPS-activated MAPK p38 phosphorylates and activates the downstream kinase MAPK-activated protein kinase 2 (MK2), which then phosphorylates serines 52 and 178 of TTP, resulting in loss of mRNA-destabilizing activity. As a consequence, mRNAs that contain binding sites for TTP are stabilized in a manner that is acutely sensitive to the activity of the MAPK p38 pathway. Dual specificity phosphatase 1 (DUSP1) dephosphorylates and inactivates MAPK p38. Dusp1-/- macrophages overexpress a number of pro-inflammatory mediators, but their genome-wide responses to LPS have not yet been described in detail. Dusp1-/- mice are exceptionally sensitive to a wide variety of inflammatory challenges, including experimental models of endotoxemia or sepsis. It has been suggested (but not yet proven) that DUSP1 controls the inflammatory response of macrophages in part via the regulation of MAPK p38 activity and TTP phosphorylation status. We generated a mouse knock-in strain, in which codons 52 and 178 of the endogenous Zfp36 gene (which encodes TTP) were mutated to alanine codons. The mutation gives rise to a constitutively active form of TTP, which cannot be inactivated via the p38 MAPK pathway. The Zfp36aa/aa strain was back-crossed against C57/BL6 for > 10 generations. We also generated a double-targeted strain in which the Zfp36 mutation was combined with disruption of the Dusp1 gene. This expression array describes LPS responses of primary mouse bone marrow-derived macrophages of four genotypes, and closely matched genetic background: wild type (Dusp1+/+ : Zfp36+/+); TTP mutant (Zfp36aa/aa); DUSP1 knock out (Dusp1-/-); and double targeted (Dusp1-/- : Zfp36aa/aa). The data provide a comprehensive picture of the impact of Dusp1 deletion or TTP mutation on the responses of primary macrophages to LPS. They also demonstrate that the excessive inflammatory responses of Dusp1-/- macrophages are largely a consequence of the phosphorylation and inactivation of TTP. Genome wide expression profiles of wild type, Dusp1-/-, Zfp36aa/aa and Dusp1-/-/Zfp36aa/aa M-CSF derived macrophages, stimulated with LPS for 1 or 4 hours
Project description:Protein degradation is an emerging therapeutic strategy with a unique molecular pharmacology that enables the disruption of all functions associated with a target. This is particularly relevant for proteins depending on molecular scaffolding, such as transcription factors or receptor tyrosine kinases (RTKs). To address tractability of multiple RTKs for chemical degradation by the E3 ligase cereblon (CRBN), we synthesized a series of phthalimide degraders based on the promiscuous kinase inhibitors sunitinib and PHA665752. While both series failed to induce degradation of their consensus targets, individual molecules displayed pronounced efficacy in leukemia cell lines. Orthogonal target identification supported by molecular docking led us to identify the translation termination factor G1 to S phase transition 1 (GSPT1) as a converging off-target resulting from inadvertent E3 ligase modulation. This research highlights the importance of monitoring degradation events that are independent of the respective targeting ligand as a unique feature of small-molecule degraders.
Project description:Here, we aim to understand the role of P38 in the airway epithelial cells response to flagellin. We report the gene expression profile of pig airway epithelial cells cultured under air-liquid conditions, pre-incubated or not with the P38 inhibitor SB203580 (20 µM, Tocris Bioscience) for 1 h and then stimulated with 100 ng/ml of a mutated flagellin (FliCΔ174-400) for 2h or 24h. Our data show that flagellin stimulation induce the expression of pro-inflammatory cytokines mainly through the NFkB pathway, with little impact of P38 inhibition in the cells response.
Project description:Glucocorticoid Receptor (GR) suppresses inflammation by activating anti-inflammatory and repressing pro-inflammatory genes. GR-interacting protein (GRIP)1 of the p160 family has emerged as a unique GR corepressor in macrophages (MΦ), however, whether GRIP1 contributes to GR-activated transcription, and what dictates its context-specific coactivator vs. corepressor properties is unknown. We report that loss of GRIP1 in human and mouse MΦ attenuated GR-mediated induction of several anti-inflammatory targets, revealing a non-redundant function of GRIP1 in coactivation. Moreover, glucocorticoid treatment of quiescent MΦ globally directed GRIP1 toward GR-bound genomic sites dominated by classic palindromic GREs, suggesting its dedicated role as a GR coactivator. Further, GRIP1 N-terminal region was phosphorylated at a serine cluster by Cyclin-Dependent Kinase (CDK)9, which was recruited into GC-induced GR:GRIP1:CDK9 ternary complexes, producing distinct GRIP1 phospho-isoforms at different GREs even associated with the same gene. Functionally, phosphorylation potentiated GRIP1 coactivator properties by facilitating its recruitment and/or creating novel protein:protein interaction surfaces in a GRE-specific manner. Strikingly, GRIP1 function as a GR corepressor was phosphorylation-independent; consistently, no phospho-GRIP1 or CDK9 was detected at GR transrepression sites near pro-inflammatory genes. Thus, liganded GR in MΦ restricts actions of its own coregulator via CDK9-mediated phosphorylation to a subset of complexes driving anti-inflammatory gene transcription.
Project description:Macrophages are key immune cells in inflammatory bowel disease (IBD) that can exhibit different phenotypes and promote inflammation. Alcohol consumption is associated with increased risk and severity of IBD. We performed in vitro and in vivo experiments with dextran sodium sulfate-induced mice colitis model, peritoneal macrophages and RAW264.7 cell line to investigate the effect and mechanism of alcohol on macrophages in colitis. Our study has found that alcohol exacerbates colitis in mice, increases the aggregation of colonic macrophages, and promotes the production of various inflammatory factors. Alcohol increases lipopolysaccharides (LPS)-induced calcium influx in macrophages, which is inhibited by the TRPV1 antagonist Capsazepine (CPZ). Alcohol and LPS together induce M2b polarization of macrophages and promote the phosphorylation and nuclear translocation of P38, ERK1/2 and NF-κB, and could be inhibited by CPZ and NOD2 inhibitor. Thus, alcohol can aggravate experimental colitis in mice and promote macrophage M2b polarization through the TRPV1-MAPK/NF-kB pathways.