Project description:Tumor-specific metabolic rewiring, intended to confer a survival advantage over non-transformed cells, often offers an opportunity to target cancers. Here, we identify deregulated expression of purine biosynthetic enzymes as a metabolic hallmark in human hepatocellular carcinomas (HCC), with the extent of enzyme upregulation a predictor of clinical outcome. We demonstrate in HCC cell lines, patient-derived xenograft (PDX) organoids and mouse models that inhibition of purine biosynthesis abrogated cancer cell proliferation and tumor growth. Mechanistically, a PI3K-E2F1 axis coordinated purine biosynthetic enzyme expression. Clinically approved inhibitors against PI3K and the purine biosynthetic rate-limiting enzyme IMPDH synergistically reduced the tumor burden in a PDX mouse model. Collectively, our results support targeting purine metabolic reprogramming as a precision therapeutic strategy for HCC patients.
Project description:We employed bulk RNA-sequencing to compare gene expression between the two major phenotypic subsets of disease-associated macrophages based on MHCII protein expression as well as tissue-resident macrophages and disease-monocytes.
Project description:Bacterial pathogens such as Salmonella enterica serovar Typhimurium can resist phagocytosis by macrophages. Here we explored the role of bacterial heme biosynthesis in phagocytosis resistance. Using transposon sequencing (Tn-seq) during Salmonella infection of macrophages, we identify a methyltransferase, SirM, that indirectly inhibits phagocytosis of bacteria. Mechanistically, sirM is activated upon interaction with macrophages and methylates HemL, a key enzyme in heme biosynthesis, resulting in upregulation of heme synthesis by Salmonella. Salmonella-derived heme inhibits Cdc42 activation in a Toll-like receptor 4 (TLR4)-dependent manner to inhibit phagocytosis. Moreover, sirM promotes macrophage death by increasing heme synthesis. Experiments in mouse models show that sirM is required for virulence and confers a competitive advantage over intestinal commensal bacteria during infection. We also found that sirM is distributed among enteric pathogens. Collectively, our findings show that bacterial heme promotes evasion of phagocyte responses and pathogenesis to confer an advantage in the host.
Project description:Proper regulation of inflammatory responses is essential for organismal health. Dysregulation can lead to accelerated development of the diseases of aging and the aging process itself. Here, we identify a novel enzymatic activity of the mitochondrial sirtuin SIRT4 as a lysine deitaconylase that regulates macrophage inflammatory responses. Itaconate is a metabolite abundantly produced in activated macrophages. We find it forms a protein modification called lysine itaconylation. Using biochemical and proteomics approaches, we demonstrate that SIRT4 efficiently removes this modification from target proteins both in vitro and in vivo. In macrophages, SIRT4 expression increases upon LPS stimulation, coinciding with elevated protein itaconylation. SIRT4-deficient macrophages exhibit significantly increased IL-1β production in response to LPS stimulation. This phenotype is intrinsic to macrophages, as demonstrated by both SIRT4 knockdown and lentiviral over-expression models. Mechanistically, we identify key enzymes in branched-chain amino acid (BCAA) metabolism as targets of hyperitaconylation in SIRT4-deficient macrophages. The BCKDH complex component dihydrolipoamide branched chain transacylase E2 (DBT) is hyperitaconylated in SIRT4KO macrophages, concomitant with reduced BCKDH activity. Physiologically, SIRT4-deficient mice exhibit significantly delayed wound healing, demonstrating a consequence of dysregulated macrophage function. Our data reveal a novel protein modification pathway in immune cells and establish SIRT4 as a critical regulator at the intersection of metabolism and inflammation. These findings have implications for understanding immune dysregulation in aging and metabolic disease.
Project description:Analysis of gene expression in explanted peritoneal macrophages from Aoah -/- and Aoah +/+ mice treated with LPS 21 days prior to harvest. Explanted peritoneal machrophages were challenged with LPS or control (PBS). The study seeks to characterize global gene expression in the state of prolonged LPS tolerance induced in mice lacking the LPS-inactivating enzyme Aoah.
Project description:Analysis of gene expression in explanted peritoneal macrophages from Aoah -/- and Aoah +/+ mice treated with LPS 21 days prior to harvest. Explanted peritoneal machrophages were challenged with LPS or control (PBS). The study seeks to characterize global gene expression in the state of prolonged LPS tolerance induced in mice lacking the LPS-inactivating enzyme Aoah. Groups of 9 C57BL/6 Aoah+/+ or Aoah-/- mice were given i.p. injections of 10 µg E. coli LPS/mouse. Twenty-one days later (when Aoah-/- mice remain tolerant and Aoah+/+ mice have recovered), peritoneal macrophages were harvested and the yields from three mice were pooled to form 3 samples per group (i.e., three samples of Aoah+/+ and Aoah-/- mice, with each sample comprised of peritoneal macrophages from 3 mice). Next day, cells were challenged with LPS or PBS and whole RNA was isolated 2 hours later and used for microarray experiments.