Project description:Activation of the STING (Stimulator of Interferon Genes) pathway by microbial or self-DNA, as well as cyclic di nucleotides (CDN), results in the induction of numerous genes that suppress pathogen replication and facilitate adaptive immunity. However, sustained gene transcription is rigidly prevented to avoid lethal STING-dependent pro-inflammatory disease by mechanisms that remain unknown. We demonstrate here that after autophagy-dependent STING delivery of TBK1 (TANK-binding kinase 1) to endosomal/lysosomal compartments and activation of transcription factors IRF3 (interferon regulatory factors 3) and NF-κB (nuclear factor kappa beta), that STING is subsequently phosphorylated by serine/threonine UNC-51-like kinase (ULK1/ATG1) and IRF3 function is suppressed. ULK1 activation occurred following disassociation from its repressor adenine monophosphate activated protein kinase (AMPK), and was elicited by CDN’S generated by the cGAMP synthase, cGAS. Thus, while CDN’s may initially facilitate STING function, they subsequently trigger negative-feedback control of STING activity, thus preventing the persistent transcription of innate immune genes. Total RNA obtained from primary STING deficient mouse embryonic fibroblast reconstituted with mSTING (W), S365A variant (A), or S365D variant (D). These cells were transfected with dsDNA (ISD) for 3 hours.
Project description:Obesity is an epidemic affecting 13% of the global population and increasing the risk of many chronic diseases. However, only several drugs are licensed for pharmacological intervention for the treatment of obesity. As a master regulator of metabolism, the therapeutic potential of AMPK is widely recognized and aggressively pursued for the treatment of metabolic diseases. We found that elaiophylin (Ela) rapidly activates AMPK in a panel of cancer cell lines, as well as primary hepatocytes and adipocytes. Meanwhile, Ela inhibits the mTORC1 complex, turning on catabolism and turning off anabolism together with AMPK. In vitro and in vivo studies showed that Ela does not activate AMPK directly; instead, it increases cellular AMP/ATP and ADP/ATP ratios, leading to AMPK phosphorylation in a LKB1-dependent manner. AMPK activation induced by Ela caused changes in diverse metabolic genes, thereby promoting glucose consumption and fatty acid oxidation. Importantly, Ela activates AMPK in mouse liver and adipose tissue. As a consequence, it reduces body weight and blood glucose levels and improves glucose and insulin tolerance in both ob/ob and high fat diet-induced obese mouse models. Our study has identified a novel AMPK activator as a candidate drug for the treatment of obesity and its associated chronic diseases.
Project description:Inflammatory diseases such as Aicardi-Goutieres Syndrome (AGS) and severe systemic lupus erythematosus (SLE) are generally lethal disorders that have been traced to defects in the exonuclease Trex1 (DNAseIII). Mice lacking Trex1 similarly die at an early age through comparable symptoms, including inflammatory myocarditis, through chronic activation of the STING (stimulator of interferon genes) pathway. Here we demonstrate that phagocytes rather than myocytes are predominantly responsible for causing inflammation, an outcome that could be alleviated following adoptive transfer of normal bone marrow into Trex1-/- mice. Trex1-/- macrophages did not exhibit significant augmented ability to produce pro-inflammatory cytokines compared to normal macrophages following exposure to STING-dependent activators, but rather appeared chronically stimulated by genomic DNA. These results shed molecular insight into inflammation and provide concepts for the design of new therapies. Total RNA obtained from wild type (WT), Trex1 deficient (TKO), STING deficient (SKO), or Trex1 and STING double deficient (STKO) mouse Heart
Project description:TP53-mutant blood cancers remain a major clinical challenge. BH3-mimetic drugs inhibit BCL-2 pro-survival proteins to promote cancer cell apoptosis. Despite acting downstream of TP53, functional TP53 is required for maximal cancer cell killing by BH3-mimetics through an unknown mechanism. Here, we report TP53 can be activated following BH3-mimetic induced mitochondrial outer membrane permeabilization, which leads to induction of BH3-only proteins, thereby potentiating the pro-apoptotic signal. TP53-deficient lymphomas lack this feed-forward loop, providing opportunities for survival and disease relapse after BH3-mimetic treatment. The therapeutic barrier imposed by defects in TP53 could be overcome by direct activation of the cGAS/STING pathway, which promotes apoptosis of blood cancer cells through TP53-independent BH3-only protein upregulation. Combining clinically relevant STING agonists with BH3-mimetics efficiently killed TP53-mutant mouse B lymphoma, human NK/T lymphoma and acute myeloid leukemia cells. This represents a promising therapy regime that can be fast-tracked to tackle TP53-mutant blood cancers in the clinic.
Project description:Inflammatory diseases such as Aicardi-Goutieres Syndrome (AGS) and severe systemic lupus erythematosus (SLE) are generally lethal disorders that have been traced to defects in the exonuclease Trex1 (DNAseIII). Mice lacking Trex1 similarly die at an early age through comparable symptoms, including inflammatory myocarditis, through chronic activation of the STING (stimulator of interferon genes) pathway. Here we demonstrate that phagocytes rather than myocytes are predominantly responsible for causing inflammation, an outcome that could be alleviated following adoptive transfer of normal bone marrow into Trex1-/- mice. Trex1-/- macrophages did not exhibit significant augmented ability to produce pro-inflammatory cytokines compared to normal macrophages following exposure to STING-dependent activators, but rather appeared chronically stimulated by genomic DNA. These results shed molecular insight into inflammation and provide concepts for the design of new therapies. Total RNA obtained from wild type murine embryonic fibroblasts (WT MEFs), Trex1 deficient MEFs (TKO) or STING and Trex1 double deficient MEFs (STKO) transfected with or without double strand DNA 90 (ISD) and examined cytokine production by these cells.
Project description:The cGAS-STING pathway forms a major component of the innate immune system. cGAS-STING signalling is induced by detection of either foreign (i.e. pathogenic) or mislocalised host double stranded (ds)DNA present within the cytosol. STING acts as the major signalling hub, where it controls activation of transcription factors IRF3 and NF-B for expression of type I interferons and inflammatory cytokines, respectively. Under resting conditions STING resides on the ER membrane. However, following activation STING traffics to the Golgi to initiate downstream signalling, and subsequently to endolysosomal regions for degradation and termination of signalling. However, while STING is known to be degraded by lysosomes, the mechanisms controlling its delivery remain poorly defined. Here we utilised a mass spectrometry approach to assess phosphorylation changes in primary macrophages following STING activation. This identified a large number of phosphorylation events in proteins involved in intracellular transport, including vesicular trafficking. We utilised high-temporal microscopy to track STING vesicular transport in live macrophages. We observed that while macrophages exhibit rapid degradation of STING (i.e., 4-6 h), basal STING protein levels return slowly (i.e., >24 h). Despite STING protein recovery, ultimately macrophages remain unresponsive to re-challenge with STING ligands. Using a combination of imaging and biochemical approaches we subsequently identify that the endosomal complexes required for transport (ESCRT) pathway detects ubiquitinated STING on endosomes, which facilitates the degradation of STING. Disrupting ESCRT recognition of STING via knockdown of the ESCRT-0 component HRS or inhibiting ESCRT function via overexpression of a dominant negative form of VPS4a enhances STING signalling and cytokine production. Therefore, we have characterised the mechanisms that controls effective termination of STING signalling. Dysregulation of STING localisation or its degradation has been implicated in several diseases including autoimmune, autoinflammatory and neuroinflammatory diseases, hence a clearer understanding of STING degradation is imperative for a better understanding of STING-dependent disease pathologies.
Project description:Chronic stimulation of innate immune pathways by microbial agents or damaged tissue is known to promote inflammation-driven tumorigenesis by unclarified mechanisms1-3. Here we demonstrate that mutagenic 7,12-dimethylbenz(a)anthracene (DMBA), etoposide or cisplatin induces nuclear DNA leakage into the cytosol to intrinsically activate STING (Stimulator of Interferon Genes) dependent cytokine production. Inflammatory cytokine levels were subsequently augmented in a STING-dependent extrinsic manner by infiltrating phagocytes purging dying cells. Consequently, STING-/- mice, or wild type mice adoptively transferred with STING-/- bone marrow, were almost completely resistant to DMBA-induced skin carcinogenesis compared to their wild type counterparts. Our data emphasizes, for the first time, a role for STING in the induction of cancer, sheds significant insight into the causes of inflammation-driven carcinogenesis, and may provide therapeutic strategies to help prevent malignant disease Total RNA obtained from wild type murine embryonic fibroblasts (WT MEFs), STING deficient MEFs (SKO), Trex1 deficient MEFs (TKO), and both STING and Trex1 deficient MEFs (STKO) treated with DMBA and examined cytokine production by these cells.