Project description:In vitro studies associated oxidative phosphorylation (OXPHOS) with anti-inflammatory macrophages, while pro-inflammatory macrophages rely on glycolysis. However, the metabolic needs of macrophages in tissues (TMFs) to fulfil their homeostatic activities are incompletely understood. Here, we identified OXPHOS as highly discriminating process among TMFs from different tissues in homeostasis by analysis of RNAseq data, in both human and mouse. Impairing OXPHOS in TMFs via Tfam deletion differentially affected TMF populations. Tfam deletion resulted in reduction of alveolar macrophages (AMs) due to impaired lipid-handling capacity, leading to increased cholesterol content and cellular stress, causing cell cycle arrest in vivo. In obesity, Tfam depletion selectively ablated pro-inflammatory lipid-handling white adipose tissue macrophages (WAT-MFs), preventing insulin resistance and hepatosteatosis. Thus, OXPHOS, rather than glycolysis, distinguishes TMF populations and is critical for the maintenance of TMFs with a high lipid-handling activity, including pro-inflammatory WAT-MFs. This could provide a selective therapeutic targeting tool.
Project description:In vitro studies associated oxidative phosphorylation (OXPHOS) with anti-inflammatory macrophages, while pro-inflammatory macrophages rely on glycolysis. However, the metabolic needs of macrophages in tissues (TMFs) to fulfil their homeostatic activities are incompletely understood. Here, we identified OXPHOS as highly discriminating process among TMFs from different tissues in homeostasis by analysis of RNAseq data, in both human and mouse. Impairing OXPHOS in TMFs via Tfam deletion differentially affected TMF populations. Tfam deletion resulted in reduction of alveolar macrophages (AMs) due to impaired lipid-handling capacity, leading to increased cholesterol content and cellular stress, causing cell cycle arrest in vivo. In obesity, Tfam depletion selectively ablated pro-inflammatory lipid-handling white adipose tissue macrophages (WAT-MFs), preventing insulin resistance and hepatosteatosis. Thus, OXPHOS, rather than glycolysis, distinguishes TMF populations and is critical for the maintenance of TMFs with a high lipid-handling activity, including pro-inflammatory WAT-MFs. This could provide a selective therapeutic targeting tool.
Project description:Dermal invasion is a hallmark of malignant melanoma. The molecular alterations driving the progression of primary melanoma to metastatic disease have been studied extensively, whereas the early progression of non-invasive primary melanoma to an invasive state is not well understood. To elucidate the mechanisms underlying the transition from radial to vertical growth, the first step in melanoma invasion, we developed a zebrafish melanoma model in which constitutive activation of ribosomal protein S6 kinase 1 (RSK1) drives tumor invasion. Transcriptomic analysis of RSK1-activated tumors identified metabolic changes, including upregulation of genes associated with oxidative phosphorylation. Vertical growth phase human melanoma cells show higher oxygen consumption and preferential utilization of glutamine compared to radial growth phase melanoma cells. Peroxisome proliferator-activated receptor gamma coactivator-1α (PGC1a has been proposed as a master regulator of tumor oxidative phosphorylation. In human primary melanoma specimens we show that PGC1a protein expression is positively associated with increased tumor thickness and expression of the proliferative marker Ki-67 and the reactive oxygen species (ROS) scavenger SCARA3. PGC1a depletion modulates cellular processes associated with primary melanoma growth and invasion, including oxidative stress. Our results support a role for PGC1a in mediating glutamine-driven OXPHOS to facilitate the invasive growth of primary melanoma.
Project description:Transcription factors are important drivers of cancer but the development of therapeutics against these factors has had limited success. We developed a stringent high-throughput chemical genetic screening platform to identify compounds that target oncogene SALL4 dependency in liver cancer. The platform comprises SALL4 low- and high-expressing endogenous cell lines, and engineered SALL4-low isogenic lines overexpressing SALL4. We identified 4 oxidative phosphorylation (OXPHOS) inhibitors, from screening 21,575 natural product extracts, that selectively reduce SALL4-dependent cell viability. ATP synthase inhibitor Oligomycin suppresses SALL4-expressing cancer in culture and in vivo. When aberrantly overexpressed in cancer, SALL4 binds ~50% of OXPHOS and other mitochondrial genes, upregulating their expression. SALL4 upregulation also functionally increases OXPHOS. Our endogenous/isogenic transcription factor-screening platform reveals a therapeutically actionable OXPHOS vulnerability in SALL4-expressing cancer.
Project description:The cellular stress response triggers a cascade of events leading to transcriptional reprogramming and a transient inhibition of global protein synthesis, which is thought to be mediated by phosphorylation of eukaryotic initiation factor-2α (eIF2α). Using mouse embryonic fibroblasts (MEFs) and the fission yeast S. pombe, we report that rapid translational arrest and cell survival in response to hydrogen peroxide-induced oxidative stress do not rely on eIF2a kinases and eIF2a phosphorylation. Rather H2O2 induces a block in elongation through phosphorylation of eukaryotic elongation factor 2 (eEF2). Kinetic and dose-response analyses uncovered crosstalk between the eIF2a and eEF2 phosphorylation pathways, indicating that, in MEFs, eEF2 phosphorylation initiates the acute shutdown in translation, which is maintained by eIF2a phosphorylation. Our results challenge the common conception that eIF2a phosphorylation is the primary trigger of translational arrest in response to oxidative stress and point to integrated control that may facilitate the survival of cancer cells.