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Iron Drives Anabolic Metabolism Through Active Histone Demethylation and mTORC1

ABSTRACT: All living cells require a minimal iron threshold to sustain anabolic metabolism. However, the mechanisms by which cells sense iron to regulate anabolic processes are unclear. Here, we report a universal eukaryotic pathway for iron sensing in which molecular iron is required to sustain active histone demethylation and maintain the expression of critical components of the pro-anabolic mTORC1 pathway. Specifically, we identify the iron-binding histone-demethylase KDM3B as an intrinsic iron sensor that regulates mTORC1 activity by demethylating H3K9me2 at enhancers of genes encoding high-affinity leucine transporters and RAPTOR. By directly suppressing leucine availability and RAPTOR levels, iron deficiency (ID) supersedes other nutrient inputs into mTORC1. This process occurs in vivo, and is not an indirect effect by canonical iron-utilizing pathways. Elevated expression of KDM3B targets is associated with reduced survival in a subset of human cancers and ID represses mTORC1 in patient-derived tumor cells and sensitizes cancer cells to chemotherapy. These data demonstrate a novel mechanism of eukaryotic iron sensing through dynamic chromatin remodeling and repression of mTORC1 mediated anabolism. Due to ancestral eukaryotes sharing homologues of KDMs and mTORC1 core components, this pathway likely predated the emergence of the other kingdom-specific nutrient sensors for mTORC1

ORGANISM(S): Homo sapiens

PROVIDER: GSE214019 | GEO | 2023/07/18

REPOSITORIES: GEO

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Iron Drives Anabolic Metabolism Through Active Histone Demethylation and mTORC1

Project description:All living cells require a minimal iron threshold to sustain anabolic metabolism. However, the mechanisms by which cells sense iron to regulate anabolic processes are unclear. Here, we report a universal eukaryotic pathway for iron sensing in which molecular iron is required to sustain active histone demethylation and maintain the expression of critical components of the pro-anabolic mTORC1 pathway. Specifically, we identify the iron-binding histone-demethylase KDM3B as an intrinsic iron sensor that regulates mTORC1 activity by demethylating H3K9me2 at enhancers of a high-affinity leucine transporter and RAPTOR. By directly suppressing leucine availability and RAPTOR levels, iron deficiency (ID) supersedes other nutrient inputs into mTORC1. This process occurs in vivo, and is not an indirect effect by canonical iron-utilizing pathways. These data demonstrate a novel mechanism of eukaryotic iron sensing through dynamic chromatin remodeling and repression of mTORC1 mediated anabolism. Due to ancestral eukaryotes sharing homologues of KDMs and mTORC1 core components, this pathway likely predated the emergence of the other kingdom-specific nutrient sensors for mTORC1.

2023-07-20 | PXD043952 | Pride

O-GlcNAcylation of Raptor transduces glucose signals to mTORC1

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Transcriptome changes associated with targeting mTORC1 in endothelial cells

Project description:Tumor metastasis, the main cause of death in cancer patients, requires outgrowth of tumor cells after their dissemination and residence in microscopic niches. Nutrient sufficiency is a determinant of such outgrowth. Fatty acids (FA) can be metabolized by cancer cells for their energetic and anabolic needs, thereby supporting metastatic progression. The vascular endothelium serves as a barrier to access of molecules into tissues, but it is unclear how fatty acid delivery to early metastatic tumors is regulated. Using a mouse model of metastatic outgrowth in the lung, we show that tumor endothelium actively promotes tumor growth by transferring FA into developing metastatic tumors. Tumor burden was significantly reduced upon endothelial-specific targeted deletion of Raptor, a unique component of the mTORC1 complex (RptorECKO). The goal of this study was to investigate how targeting Raptor/mTORC1 impacts endothelial cells.

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Proteomic analysis of Raptor-proximal proteins in U2OS cells

Project description:The mammalian target of rapamycin complex 1 (mTORC1) is a key nutrient-sensing hub and a master regulator of cellular growth and metabolism. Activation of mTORC1 by amino acids and growth factors requires its recruitment to the lysosomes. Furthermore, lysosomal distribution has been shown to be intimately involved in the control of mTORC1, where localisation of lysosomes near plasma membrane increases mTORC1 activity. However, the underlying mechanisms by which lysosomal positioning impacts on mTORC1 signalling are not well understood. To understand better the spatial associations of mTORC1, we analysed the proximal ‘interactome’ of the constitutive component of mTORC1, Raptor, using BioID2-based proximity labelling and MS-based proteomics.

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RNA-seq of metformin treatment in primary murine hepatocytes in WT, Raptor Ser-Ala mutant, Tsc2-null, Raptor mutant;Tsc2-null, and Ampk-null cells

Project description:Despite being the frontline therapy for Type 2 diabetes, the mechanisms of action of the biguanide drug metformin are still being discovered. In particular, the detailed molecular interplays between the AMPK and the mTORC1 pathway in the hepatic benefits of metformin are still ill-defined. Metformin-dependent activation of AMPK classically inhibits mTORC1 via TSC/RHEB. But several lines of evidence suggest additional mechanisms at play in metformin inhibition of mTORC1. Here we investigated the role of direct AMPK-mediated serine phosphorylation of RAPTOR in a new RaptorAA mouse model, in which AMPK phospho-serine sites Ser722 and Ser792 of RAPTOR were mutated to alanine. Metformin treatment of primary hepatocytes and intact murine liver requires AMPK regulation of both RAPTOR and TSC2 to fully inhibit mTORC1, and this regulation is critical for the transcriptional response to metformin. Transcriptionally, AMPK and mTORC1 were both important for regulation of anabolic metabolism and inflammatory programs triggered by metformin treatment.

2023-08-10 | GSE157048 | GEO

Raptor/mTORC1-dependent metabolic programming of exit from quiescence underlies T cell activation and fate decisions

Project description:Naïve T cells respond to antigen stimulation by exiting from quiescence into clonal expansion and functional differentiation, but the control mechanism is elusive. Here we describe that Raptor/mTORC1-dependent metabolic reprogramming is a central determinant of this transitional process. Loss of Raptor abrogates T cell priming and Th2 cell differentiation, although Raptor function is less important for continuous proliferation of actively cycling cells. mTORC1 coordinates multiple metabolic programs in T cells including glycolysis, lipid synthesis and oxidative phosphorylation to mediate antigen-triggered exit from quiescence. mTORC1 further links glucose metabolism to the initiation of Th2 differentiation by orchestrating cytokine receptor expression and cytokine responsiveness. Activation of Raptor/mTORC1 integrates T cell receptor (TCR) and CD28 co-stimulatory signals in antigen-stimulated T cells. Our studies identify a Raptor/mTORC1-dependent pathway linking signal-dependent metabolic reprogramming to quiescence exit, and this in turn coordinates lymphocyte activation and fate decisions in adaptive immunity. We used microarrays to explore the gene expression profiles differentially expressed in CD4+ T-cells from wild-type (WT) and CD4(cre) x Raptor(fl/fl) mice before and after stimulation with anti CD3/CD28 antibodies.

2014-01-27 | E-GEOD-51668 | biostudies-arrayexpress

RNA-seq of metformin treatment in liver in WT, Raptor Ser-Ala mutant, Tsc2-null, Raptor mutant;Tsc2-null, and Ampk-null

Project description:Despite being the frontline therapy for Type 2 diabetes, the mechanisms of action of the biguanide drug metformin are still being discovered. In particular, the detailed molecular interplays between the AMPK and the mTORC1 pathway in the hepatic benefits of metformin are still ill-defined. Metformin-dependent activation of AMPK classically inhibits mTORC1 via TSC/RHEB. But several lines of evidence suggest additional mechanisms at play in metformin inhibition of mTORC1. Here we investigated the role of direct AMPK-mediated serine phosphorylation of RAPTOR in a new RaptorAA mouse model, in which AMPK phospho-serine sites Ser722 and Ser792 of RAPTOR were mutated to alanine. Metformin treatment of intact murine liver requires AMPK regulation of both RAPTOR and TSC2 to fully inhibit mTORC1, and this regulation is critical for the transcriptional response to metformin. Transcriptionally, AMPK and mTORC1 were both important for regulation of anabolic metabolism and inflammatory programs triggered by metformin treatment. The hepatic transcriptional response in mice on high fat diet treated with metformin was largely ablated by AMPK-deficiency under the conditions examined, indicating the essential role of this kinase and its targets in metformin action in vivo.

2023-08-10 | GSE157049 | GEO

HEK-293T LC-MS/MS

Project description:We established two in vitro cell-free systems to mimic the activation of mTORC1 and autophagy by monitoring the translocation of two readout proteins Raptor and ATG14. Based on the two systems, we further screened the potential regulators involved in the leucine-mediated mTORC1 and autophagy pathways using comparative proteomics strategy.

2022-03-03 | PXD007811 | Pride

Effects of targeting endothelial mTORC1 on metastatic tumor cells

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mTORC1 maintains renal tubular homeostasis and is essential in response to ischemic stress

Project description:The mechanistic target of rapamycin mTORC1 is a key regulator of cell metabolism and autophagy. Despite widespread clinical use of mTOR inhibitors, the role of mTORC1 in renal tubular function and kidney homeostasis remains elusive. By utilizing constitutive and inducible deletion of conditional Raptor alleles in renal tubular epithelial cells, we discovered that mTORC1 deficiency caused a marked concentrating defect, loss of tubular cells and slowly progressive renal fibrosis. Transcriptional profiling revealed that mTORC1 maintains renal tubular homeostasis by controlling mitochondrial metabolism and biogenesis as well as transcellular transport processes involved in counter-current multiplication and urine concentration. Although mTORC2 partially compensated the loss of mTORC1, exposure to ischemia and reperfusion injury exaggerated the tubular damage in mTORC1-deficient mice, and caused pronounced apoptosis, diminished proliferation rates and delayed recovery. These findings identify mTORC1 as an essential regulator of tubular energy metabolism and as a crucial component of ischemic stress responses. Pharmacological inhibition of mTORC1 likely affects tubular homeostasis, and may be particularly deleterious if the kidney is exposed to acute injury. Furthermore, the combined inhibition of mTORC1 and mTORC2 may increase the susceptibility to renal damage. Raptor fl/fl*KspCre and Raptor fl/fl animals were sacrificed at P14 before the development of an overt functional phenotype. Kidneys were split in half and immediately snap frozen in liquid nitrogen.

2014-06-09 | E-GEOD-54417 | biostudies-arrayexpress

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