Glycolysis Promotes Phosphoinositide 3-Kinase Signaling In Support of T Helper 17 Cell-Mediated Autoimmunity
Ontology highlight
ABSTRACT: T helper (Th) cell differentiation is driven by antigen and accessory signals that activate phosphoinositide 3-kinase (PI3K) to induce transcriptional and metabolic reprogramming including aerobic glycolysis (the Warburg effect). Here, we show that ATP generated through glycolysis fuels PI3K signaling to promote pathogenic Th17 cell responses. Mice with T cell-specific ablation of the glycolytic enzyme lactate dehydrogenase A (LDHA) were resistant to Th17 cell-mediated experimental autoimmune encephalomyelitis in association with defective T cell activation, migration, proliferation, and differentiation. LDHA deficiency crippled the cellular redox balance and inhibited ATP production causing attenuated phosphoinositide (3,4,5)-trisphosphate generation, and diminished activation of the Akt kinase and phosphorylation of its transcription factor target Foxo1. Th17 cell-specific expression of an Akt-insensitive Foxo1 mutant recapitulated the Th17 cell differentiation defects caused by LDHA deficiency. Thus, PI3K signaling and glycolytic bioenergetics constitute a positive feedback regulatory circuit essential for Th17 cell-mediated autoimmunity.
Project description:Upon antigen stimulation, the bioenergetic demands of T cells increase dramatically over the resting state. Although a role for the metabolic switch to glycolysis has been suggested to support increased anabolic activities and facilitate T cell growth and proliferation, whether cellular metabolism controls T cell lineage choices remains poorly understood. Here we report that the glycolytic pathway is actively regulated during the differentiation of inflammatory TH17 and Foxp3-expressing regulatory T cells (Treg), and controls cell fate determination. TH17 but not Treg-inducing conditions resulted in strong upregulation of the glycolytic activity and induction of glycolytic enzymes. Blocking glycolysis inhibited TH17 development while promoting Treg cell generation. Moreover, the transcription factor hypoxia-inducible factor 1a (HIF1a) was selectively expressed in TH17 cells and its induction required signaling through mTOR, a central regulator of cellular metabolism. HIF1a-dependent transcriptional program was important for mediating glycolytic activity, thereby contributing to the lineage choices between TH17 and Treg cells. Lack of HIF1a resulted in diminished TH17 development but enhanced Treg differentiation, and protected mice from autoimmune CNS inflammation. Our studies demonstrate that HIF1a-dependent glycolytic pathway orchestrates a metabolic checkpoint for the differentiation of TH17 and Treg cells. Naïve CD4 T cells from wild-type and HIF1a-deficient mice (in triplicates each group) were differentiated under TH17 conditions for 2.5 days, and RNA was analyzed by microarrays.
Project description:Mosca2012 - Central Carbon Metabolism Regulated by AKT
The role of the PI3K/Akt/PKB signalling pathway in oncogenesis has been extensively investigated and altered expression or mutations of many components of this pathway have been implicated in human cancers. Indeed, expression of constitutively active forms of Akt/PKB can prevent cell death upon growth factor withdrawal. PI3K/Akt/mTOR-mediated survival relies on a profound metabolic adaptation, including aerobic glycolysis. Here, the link between the PI3K/Akt/mTOR pathway, glycolysis, lactic acid production and nucleotide biosynthesis has been modelled, considering two states - high and low PI3K/Akt/mTOR activity. The high PI3K/Akt/mTOR activity represents cancer cell line where PI3K/Akt/mTOR promotes a high rate of glucose metabolism (condition H) and the low PI3K/Akt/mTOR activity is characterised by a lower glycolytic rate due to a reduced PI3K/Akt/mTOR signal (condition L). This model corresponds to the high PI3K/Akt/mTOR signal (condition H).
This model is described in the article:
Computational Modelling of the Metabolic States Regulated by the Kinase Akt.
Mosca E, Alfieri R, Maj C, Bevilacqua A, Canti G, Milanesi L.
Frontiers in Systems Biology. 2012 Oct 13
Abstract:
Signal transduction pathways and gene regulation determine a major reorganization of metabolic activities in order to support cell proliferation. Protein Kinase B (PKB), also known as Akt, participates in the PI3K/Akt/mTOR pathway, a master regulator of aerobic glycolysis and cellular biosynthesis, two activities shown by both normal and cancer proliferating cells. Not surprisingly considering its relevance for cellular metabolism, Akt/PKB is often found hyperactive in cancer cells. In the last decade, many efforts have been made to improve the understanding of the control of glucose metabolism and the identification of a therapeutic window between proliferating cancer cells and proliferating normal cells. In this context, we have modelled the link between the PI3K/Akt/mTOR pathway, glycolysis, lactic acid production and nucleotide biosynthesis. We used a computational model in order to compare two metabolic states generated by the specific variation of the metabolic fluxes regulated by the activity of the PI3K/Akt/mTOR pathway. One of the two states represented the metabolism of a growing cancer cell characterised by aerobic glycolysis and cellular biosynthesis, while the other state represented the same metabolic network with a reduced glycolytic rate and a higher mitochondrial pyruvate metabolism, as reported in literature in relation to the activity of the PI3K/Akt/mTOR. Some steps that link glycolysis and pentose phosphate pathway revealed their importance for controlling the dynamics of cancer glucose metabolism.
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Project description:Activated phosphoinositide 3-kinase (PI3K)-AKT signaling appears to be an obligate event in the development of cancer. The highly related members of the mammalian FoxO transcription factor family, FoxO1, FoxO3, and FoxO4, represent one of several effector arms of PI3K-AKT signaling, prompting genetic analysis of the role of FoxOs in the neoplastic phenotypes linked to PI3K-AKT activation. While germline or somatic deletion of up to five FoxO alleles produced remarkably modest neoplastic phenotypes, broad somatic deletion of all FoxOs engendered a progressive cancer-prone condition characterized by thymic lymphomas and hemangiomas, demonstrating that the mammalian FoxOs are indeed bona fide tumor suppressors. Transcriptome and promoter analyses of differentially affected endothelium identified direct FoxO targets and revealed that FoxO regulation of these targets in vivo is highly context-specific, even in the same cell type. Functional studies validated Sprouty2 and PBX1, among others, as FoxO-regulated mediators of endothelial cell morphogenesis and vascular homeostasis. Mice were engineered with negative control (MxCre- Fk1 L/L Fk2 L/L Afx L/L) and experimental (MxCre+ Fk1 L/L Fk2 L/L Afx L/L) genotypes. RNAs were isolated from Lung endothelial cells (2 negative controls, 2 experimental), liver sinusoidal endothelial cells (3 negative controls, 3 experimental) and thymus cells (2 negative controls, 2 experimental), and profiled on Affymetrix Mouse Genome 430 2.0 Array.
Project description:It is well known that some pathogenic cells have enhanced glycolysis, the regulatory network leading to increased glycolysis are not well characterized. Here, we show that CNS-infiltrated pathogenic TH17 cells from diseased mice specifically upregulate glycolytic pathway genes compared to homeostatic intestinal TH17 cells. Bioenergetic assay and metabolomics analyses indicate that in vitro derived pathogenic TH17 cells are highly glycolytic compared to nonpathogenic TH17 cells. Chromatin landscape analyses demonstrate TH17 cells in vivo show distinct chromatin states, and pathogenic TH17 cells show enhanced chromatin accessibility at glycolytic genes with NF-kB binding sites. Mechanistic studies reveal that miR-21 targets the E3 ubiquitin ligase Peli1-c-Rel pathway to promote glucose metabolism of pathogenic TH17 cells. Therapeutic targeting c-Rel-mediated glycolysis in pathogenic TH17 cells represses autoimmune diseases. These findings extend our understanding of the regulation TH17 cell glycolysis in vivo and provide insights for future therapeutic intervention to TH17 cell mediated autoimmune diseases.
Project description:Activated phosphoinositide 3-kinase (PI3K)-AKT signaling appears to be an obligate event in the development of cancer. The highly related members of the mammalian FoxO transcription factor family, FoxO1, FoxO3, and FoxO4, represent one of several effector arms of PI3K-AKT signaling, prompting genetic analysis of the role of FoxOs in the neoplastic phenotypes linked to PI3K-AKT activation. While germline or somatic deletion of up to five FoxO alleles produced remarkably modest neoplastic phenotypes, broad somatic deletion of all FoxOs engendered a progressive cancer-prone condition characterized by thymic lymphomas and hemangiomas, demonstrating that the mammalian FoxOs are indeed bona fide tumor suppressors. Transcriptome and promoter analyses of differentially affected endothelium identified direct FoxO targets and revealed that FoxO regulation of these targets in vivo is highly context-specific, even in the same cell type. Functional studies validated Sprouty2 and PBX1, among others, as FoxO-regulated mediators of endothelial cell morphogenesis and vascular homeostasis.
Project description:FOXO1 acts as a tumor suppressor in solid tumors. The oncogenic PI3K pathway suppresses FOXO1 transcriptional activity by enforcing its nuclear exclusion upon AKT-mediated phosphorylation. We show here abundant nuclear expression of FOXO1 in Burkitt lymphoma (BL), a germinal center (GC) B cell derived lymphoma whose pathogenesis is linked to PI3K activation. Recurrent FOXO1 mutations which prevent AKT targeting and lock the transcription factor in the nucleus are used by BL to circumvent mutual exclusivity between PI3K and FOXO1 activation. Using genome editing in human and mouse lymphomas in which MYC and PI3K cooperate synergistically in tumor development we demonstrate pro-proliferative and anti-apoptotic activity of FOXO1 in BL and identify its nuclear localization as an oncogenic event in GC B cell derived lymphomagenesis.
Project description:The transcription factor FOXO1 directs germinal center (GC) polarity and supports affinity maturation by silencing immune activation programs in GC B cells. Recurrent somatic mutations in GC-derived B cell non-Hodgkin lymphomas (B-NHL) often target and reportedly activate FOXO1 by preventing its negative regulation by PI3K. Herein, using ad hoc mouse models, engineered cell lines and primary tumor specimens, we show instead that FOXO1 mutant proteins display altered transcriptional activities suggestive of partial loss-of-function. These defects drive simultaneous hyperactivation of signaling pathways (Stress Activated Protein Kinase -SAPK/JNK, Phosphoinositide 3-kinase -PI3K/AKT) and gene expression programs typically activated in GC B cells upon positive selection. Such changes confer mutant B cells with competitive advantages in response to key immune signals, leading to abnormal amplification of GC responses. Evidence of these FOXO1 ‘mutant’ gene programs can be found in a fraction of human B-NHL and predict clinical outcome, thus implying the frequent co-option of positive selection programs during GC-derived B-NHL pathogenesis.
Project description:The transcription factor FOXO1 directs germinal center (GC) polarity and supports affinity maturation by silencing immune activation programs in GC B cells. Recurrent somatic mutations in GC-derived B cell non-Hodgkin lymphomas (B-NHL) often target and reportedly activate FOXO1 by preventing its negative regulation by PI3K. Herein, using ad hoc mouse models, engineered cell lines and primary tumor specimens, we show instead that FOXO1 mutant proteins display altered transcriptional activities suggestive of partial loss-of-function. These defects drive simultaneous hyperactivation of signaling pathways (Stress Activated Protein Kinase -SAPK/JNK, Phosphoinositide 3-kinase -PI3K/AKT) and gene expression programs typically activated in GC B cells upon positive selection. Such changes confer mutant B cells with competitive advantages in response to key immune signals, leading to abnormal amplification of GC responses. Evidence of these FOXO1 ‘mutant’ gene programs can be found in a fraction of human B-NHL and predict clinical outcome, thus implying the frequent co-option of positive selection programs during GC-derived B-NHL pathogenesis.
Project description:The transcription factor FOXO1 directs germinal center (GC) polarity and supports affinity maturation by silencing immune activation programs in GC B cells. Recurrent somatic mutations in GC-derived B cell non-Hodgkin lymphomas (B-NHL) often target and reportedly activate FOXO1 by preventing its negative regulation by PI3K. Herein, using ad hoc mouse models, engineered cell lines and primary tumor specimens, we show instead that FOXO1 mutant proteins display altered transcriptional activities suggestive of partial loss-of-function. These defects drive simultaneous hyperactivation of signaling pathways (Stress Activated Protein Kinase -SAPK/JNK, Phosphoinositide 3-kinase -PI3K/AKT) and gene expression programs typically activated in GC B cells upon positive selection. Such changes confer mutant B cells with competitive advantages in response to key immune signals, leading to abnormal amplification of GC responses. Evidence of these FOXO1 ‘mutant’ gene programs can be found in a fraction of human B-NHL and predict clinical outcome, thus implying the frequent co-option of positive selection programs during GC-derived B-NHL pathogenesis.
Project description:One major effect of PI3-kinase activation downstream of the serine/threonine kinase Akt is the phosphorylation of the transcription factor FOXO1 and its neutralization. FOXO1 has several ubiquitous targets genes in many cell types that control cell quiescence, oxydative stress or apoptosis. However, it has been demonstrated that FOXO1 also has specific targets depending of the cellular context. The role of FOXO1 to regulate specific genes in T lymphocytes has not been investigated yet. To examine this point, we used the CD4+ leukemia Jurkat T-cell line, in which the PI3K pathway is constitutively turned-on and FOXO1 transcriptional activity strongly repressed. These cells were transduced with lentiviruses coding for a constitutively active form of FOXO1 fused to GFP and having the three AKT phosphorylation sites mutated to alanine (FOXO1-AAA-GFP) to restore its transcriptional activity. GFP-transduced cells were used as a control and the gene activation levels in the two cell populations analyzed 48 hours post-infection.