Pyruvate dehydrogenase fuels a critical citrate pool that is essential for Th17 cell effector functions (ATAC-Seq)
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ABSTRACT: Pyruvate dehydrogenase (PDH) is the central enzyme connecting glycolysis and the tricarboxylic acid (TCA) cycle. The importance of PDH function in Th17 cells is unknown. Here, we show that PDH is essential for the generation of a unique glucose-derived citrate pool needed for Th17 cell proliferation, survival and effector function. In vivo, mice harboring a T cell-specific deletion of PDH were less susceptible to developing experimental autoimmune encephalomyelitis. Mechanistically, the absence of PDH in Th17 cells increased glutaminolysis, glycolysis, and lipid uptake in an mTOR-dependent manner. However, cellular citrate remained critically low in mutant Th17 cells, which interfered with oxidative phosphorylation (OXPHOS), lipid synthesis and histone acetylation crucial for the transcription of Th17 signature genes. Increasing cellular citrate in PDH-deficient Th17 cells restored their metabolism and function, identifying a metabolic feedback loop within central carbon metabolism that may offer possibilities for therapeutically targeting Th17 cell-driven autoimmunity.
Project description:Pyruvate dehydrogenase (PDH) is the central enzyme connecting glycolysis and the tricarboxylic acid (TCA) cycle. The importance of PDH function in Th17 cells is unknown. Here, we show that PDH is essential for the generation of a unique glucose-derived citrate pool needed for Th17 cell proliferation, survival and effector function. In vivo, mice harboring a T cell-specific deletion of PDH were less susceptible to developing experimental autoimmune encephalomyelitis. Mechanistically, the absence of PDH in Th17 cells increased glutaminolysis, glycolysis, and lipid uptake in an mTOR-dependent manner. However, cellular citrate remained critically low in mutant Th17 cells, which interfered with oxidative phosphorylation (OXPHOS), lipid synthesis and histone acetylation crucial for the transcription of Th17 signature genes. Increasing cellular citrate in PDH-deficient Th17 cells restored their metabolism and function, identifying a metabolic feedback loop within central carbon metabolism that may offer possibilities for therapeutically targeting Th17 cell-driven autoimmunity.
Project description:Pyruvate dehydrogenase (PDH) is the central enzyme connecting glycolysis and the tricarboxylic acid (TCA) cycle. The importance of PDH function in Th17 cells is unknown. Here, we show that PDH is essential for the generation of a unique glucose-derived citrate pool needed for Th17 cell proliferation, survival and effector function. In vivo, mice harboring a T cell-specific deletion of PDH were less susceptible to developing experimental autoimmune encephalomyelitis. Mechanistically, the absence of PDH in Th17 cells increased glutaminolysis, glycolysis, and lipid uptake in an mTOR-dependent manner. However, cellular citrate remained critically low in mutant Th17 cells, which interfered with oxidative phosphorylation (OXPHOS), lipid synthesis and histone acetylation crucial for the transcription of Th17 signature genes. Increasing cellular citrate in PDH-deficient Th17 cells restored their metabolism and function, identifying a metabolic feedback loop within central carbon metabolism that may offer possibilities for therapeutically targeting Th17 cell-driven autoimmunity.
Project description:Microtubule (MT)-based transport is an evolutionary conserved processed finely tuned by posttranslational modifications. Among them, tubulin acetylation, which is catalyzed by the α-tubulin N-acetyltransferase 1, Atat1, facilitates the recruitment and processivity of molecular motors along MT tracks. However, the mechanisms that controls Atat1 activity remains poorly understood. Here we show that a pool of vesicular ATP-citrate lyase Acly acts as a rate limiting enzyme to modulate Atat1 activity by controlling availability of Acetyl-CoA. In addition, we showed that Acly expression is reduced upon loss of Elongator activity, further connecting Elongator to Atat1 in the pathway regulating -tubulin acetylation and MT-dependent transport in projection neurons across species. Remarkably, comparable defects occur in fibroblasts from Familial Dysautonomia (FD) patients bearing an autosomal recessive mutation in the gene coding for the Elongator subunit ELP1. Our data may thus shine new light on the pathophysiological mechanisms underlying FD.
Project description:Cytotrophoblasts fuse to form and renew syncytiotrophoblasts necessary to maintain placental health throughout gestation. During cytotrophoblast to syncytiotrophoblast differentiation, cells undergo regulated metabolic and transcriptional reprogramming. Mitochondria play a critical role in differentiation events in cellular systems, thus we hypothesized that mitochondrial metabolism played a central role in trophoblast differentiation. In this work, we employed static and stable isotope tracing untargeted metabolomics methods together with gene expression and histone acetylation studies in an established cell culture model of trophoblast differentiation. Trophoblast differentiation was associated with increased abundance of the TCA cycle intermediates citrate and α-ketoglutarate. Citrate was preferentially exported from mitochondria in the undifferentiated state but was retained to a larger extent within mitochondria upon differentiation. Correspondingly, differentiation was associated with decreased expression of the mitochondrial citrate transporter (CIC). CRISPR/Cas9 disruption of the mitochondrial citrate carrier showed that CIC is required for biochemical differentiation of trophoblast. Loss of CIC resulted in broad alterations in gene expression and histone acetylation. These gene expression changes were partially rescued through acetate supplementation. Taken together, these results highlight a central role for mitochondrial citrate metabolism in the orchestration of histone acetylation and gene expression during trophoblast differentiation.
Project description:Autophagy is a cellular and energy homeostatic mechanism that contributes to maintain the number of primordial follicles, germ cell survival, and anti-ovarian aging. However, it remains unknown whether autophagy in granulosa cells affects the oocyte maturation. Here, we show a clear tendency of reduced autophagy level in human granulosa cell from women of advanced maternal age, implying a potential negative correlation between autophagy level and oocyte quality. We therefore established a co-culture system and show that either pharmacological inhibition or genetic ablation of autophagy in granulosa cells negatively affect the oocyte quality and fertilization ability. Moreover, our metabolomics analysis indicates that the adverse impact of autophagy impairment on oocyte quality is mediated by downregulated citrate levels, while exogenous supplementation of citrate can significantly restore the oocyte maturation. In molecular level, we found ATP citrate lyase (Acly), which is a crucial enzyme catalyzing the cleavage of citrate, was preferentially associated with K63-linked ubiquitin chains and recognized by the autophagy receptor protein SQSTM1/p62 for the selective autophagic degradation. In human follicles, autophagy levels in granulosa cells was downregulated with maternal aging, accompanied by decreased citrate in the follicular fluid, implying a potential correlation between citrate metabolism and oocyte quality. We also show that elevated citrate levels in porcine follicular fluid promote oocyte maturation. Collectively, our data reveal that autophagy in granulosa cells is a beneficial mechanism to maintain a certain degree of citrate by selectively targeting Acly during oocyte maturation.
Project description:Macrophages represent a major immune cell population in atherosclerotic plaques and play central role in the progression of this lipid-driven chronic inflammatory disease. Targeting immunometabolism is proposed as a strategy to revert aberrant macrophage activation to improve disease outcome. Here, we show ATP citrate lyase (Acly) to be activated in inflammatory macrophages and human atherosclerotic plaques. We demonstrate that myeloid Acly deficiency induces a stable plaque phenotype characterized by increased collagen deposition and fibrous cap thickness, along with a smaller necrotic core. In-depth functional, lipidomic, and transcriptional characterization indicate deregulated fatty acid and cholesterol biosynthesis and reduced liver X receptor (LXR) activation within the macrophages in vitro. This results in macrophages that are more prone to undergo apoptosis, whilst presenting increased phagocytosis of apoptotic cells. Together, our results indicate that targeting macrophage metabolism improves atherosclerosis outcome and we reveal Acly as a promising therapeutic target to stabilize atherosclerotic plaques.
Project description:The endothelium is a major target of the proinflammatory cytokine, tumor necrosis factor alpha (TNFα). Exposure of endothelial cells (EC) to proinflammatory stimuli leads to an increase in mitochondrial metabolism, however, the function and regulation of elevated mitochondrial metabolism in EC in response to pro-inflammatory cytokines remains unclear. Using high-resolution metabolomics and 13C-glucose labeled flux techniques, we demonstrate that pyruvate dehydrogenase activity (PDH) and tricarboxylic acid cycle flux is elevated in human umbilical vein ECs (HUVECs) in response to overnight (16 hrs) treatment with TNFα (10 ng/mL). Mechanistic studies indicate that TNFα mediates these metabolic changes via mitochondrial specific protein degradation of pyruvate dehydrogenase kinase 4 (PDK4, inhibitor of PDH) by the Lon protease via an NF-κB dependent mechanism. Using RNA sequencing following siRNA mediated knockdown of the catalytically active subunit of PDH, PDHE1a (PDHA1 gene), we show that PDH flux controls the transcription of approximately one-third of the genes that are upregulated by TNFa stimulation. Notably, TNFa induced PDH flux regulates a unique signature of proinflammatory mediators (cytokines and chemokines) but not inducible adhesion molecules. Using metabolomics and ChIP sequencing (H3AcK27), we demonstrate that TNFα induced PDH flux promotes histone acetylation of specific gene sets via citrate accumulation and ATP-citrate lyase activity. Together, these results indicate that targeting endothelial glucose oxidation and/or acetyl CoA generation may offer a novel therapeutic strategy in the treatment of vascular inflammation.
Project description:The endothelium is a major target of the proinflammatory cytokine, tumor necrosis factor alpha (TNFα). Exposure of endothelial cells (EC) to proinflammatory stimulileads to an increase in mitochondrial metabolism, however, the function and regulation of elevated mitochondrial metabolism in EC in response to pro-inflammatory cytokines remains unclear. Using high-resolution metabolomics and13C-glucose labeled flux techniques, we demonstrate thatpyruvate dehydrogenase activity (PDH) and tricarboxylic acid cycle flux is elevated in human umbilical vein ECs (HUVECs) in response to overnight (16 hrs) treatment withTNFα (10 ng/mL).Mechanistic studies indicate thatTNFα mediates these metabolic changes via mitochondrial specific protein degradation of pyruvate dehydrogenase kinase 4 (PDK4, inhibitor of PDH) by the Lon protease via an NF-κB dependent mechanism. Using RNA sequencing following siRNA mediated knockdown of thecatalytically active subunit of PDH, PDHE1a(PDHA1 gene), we show that PDH fluxcontrols the transcription of approximately one-third of the genes that are upregulated by TNFastimulation. Notably, TNFainduced PDHflux regulates a unique signature of proinflammatory mediators (cytokines and chemokines) but not inducible adhesion molecules.Using metabolomics and ChIP sequencing (H3AcK27), we demonstrate that TNFα induced PDH flux promotes histone acetylation of specific gene sets via citrate accumulation and ATP-citrate lyase activity.Together, these resultsindicate that targeting endothelial glucose oxidation and/or acetyl CoA generation may offer a novel therapeutic strategy in the treatment of vascular inflammation.