RESUMEN
Activated natural killer (NK) cells engage in a robust metabolic response that is required for normal effector function. Using genetic, pharmacological and metabolic analyses, we demonstrated an essential role for Srebp transcription factors in cytokine-induced metabolic reprogramming of NK cells that was independent of their conventional role in the control of lipid synthesis. Srebp was required for elevated glycolysis and oxidative phosphorylation and promoted a distinct metabolic pathway configuration in which glucose was metabolized to cytosolic citrate via the citrate-malate shuttle. Preventing the activation of Srebp or direct inhibition of the citrate-malate shuttle inhibited production of interferon-γ and NK cell cytotoxicity. Thus, Srebp controls glucose metabolism in NK cells, and this Srebp-dependent regulation is critical for NK cell effector function.
Asunto(s)
Glucosa/metabolismo , Glucólisis , Células Asesinas Naturales/metabolismo , Proteína 1 de Unión a los Elementos Reguladores de Esteroles/metabolismo , Proteína 2 de Unión a Elementos Reguladores de Esteroles/metabolismo , Animales , Proliferación Celular , Citocinas/metabolismo , Citometría de Flujo , Humanos , Immunoblotting , Células Asesinas Naturales/inmunología , Lípidos/biosíntesis , Fosforilación Oxidativa , Subgrupos de Linfocitos T/inmunología , Subgrupos de Linfocitos T/metabolismoRESUMEN
Cellular metabolism is dynamically regulated in NK cells and strongly influences their responses. Metabolic dysfunction is linked to defective NK cell responses in diseases such as obesity and cancer. The transcription factors, sterol regulatory element binding protein (SREBP) and cMyc, are crucial for controlling NK cell metabolic and functional responses, though the mechanisms involved are not fully understood. This study reveals a new role for SREBP in NK cells in supporting de novo polyamine synthesis through facilitating elevated cMyc expression. Polyamines have diverse roles and their de novo synthesis is required for NK cell glycolytic and oxidative metabolism and to support optimal NK cell effector functions. When NK cells with impaired SREBP activity were supplemented with exogenous polyamines, NK cell metabolic defects were not rescued but these NK cells displayed significant improvement in some effector functions. One role for polyamines is in the control of protein translation where spermidine supports the posttranslational hypusination of translation factor eIF5a. Pharmacological inhibition of hypusination also impacts upon NK cell metabolism and effector function. Considering recent evidence that cholesterol-rich tumor microenvironments inhibit SREBP activation and drive lymphocyte dysfunction, this study provides key mechanistic insight into this tumor-evasion strategy.
Asunto(s)
Células Asesinas Naturales/inmunología , Células Asesinas Naturales/metabolismo , Poliaminas/metabolismo , Animales , Células Cultivadas , Femenino , Glucólisis , Células Asesinas Naturales/efectos de los fármacos , Lisina/análogos & derivados , Lisina/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Fosforilación Oxidativa , Factores de Iniciación de Péptidos/metabolismo , Poliaminas/farmacología , Proteínas Proto-Oncogénicas c-myc/genética , Proteínas Proto-Oncogénicas c-myc/metabolismo , Proteínas de Unión al ARN/metabolismo , Proteínas de Unión a los Elementos Reguladores de Esteroles/deficiencia , Proteínas de Unión a los Elementos Reguladores de Esteroles/metabolismo , Factor 5A Eucariótico de Iniciación de TraducciónRESUMEN
BACKGROUND: In renal Fanconi's syndrome, dysfunction in proximal tubular cells leads to renal losses of water, electrolytes, and low-molecular-weight nutrients. For most types of isolated Fanconi's syndrome, the genetic cause and underlying defect remain unknown. METHODS: We clinically and genetically characterized members of a five-generation black family with isolated autosomal dominant Fanconi's syndrome. We performed genomewide linkage analysis, gene sequencing, biochemical and cell-biologic investigations of renal proximal tubular cells, studies in knockout mice, and functional evaluations of mitochondria. Urine was studied with the use of proton nuclear magnetic resonance ((1)H-NMR) spectroscopy. RESULTS: We linked the phenotype of this family's Fanconi's syndrome to a single locus on chromosome 3q27, where a heterozygous missense mutation in EHHADH segregated with the disease. The p.E3K mutation created a new mitochondrial targeting motif in the N-terminal portion of EHHADH, an enzyme that is involved in peroxisomal oxidation of fatty acids and is expressed in the proximal tubule. Immunocytofluorescence studies showed mistargeting of the mutant EHHADH to mitochondria. Studies of proximal tubular cells revealed impaired mitochondrial oxidative phosphorylation and defects in the transport of fluids and a glucose analogue across the epithelium. (1)H-NMR spectroscopy showed elevated levels of mitochondrial metabolites in urine from affected family members. Ehhadh knockout mice showed no abnormalities in renal tubular cells, a finding that indicates a dominant negative nature of the mutation rather than haploinsufficiency. CONCLUSIONS: Mistargeting of peroxisomal EHHADH disrupts mitochondrial metabolism and leads to renal Fanconi's syndrome; this indicates a central role of mitochondria in proximal tubular function. The dominant negative effect of the mistargeted protein adds to the spectrum of monogenic mechanisms of Fanconi's syndrome. (Funded by the European Commission Seventh Framework Programme and others.).
Asunto(s)
Síndrome de Fanconi/genética , Túbulos Renales Proximales/metabolismo , Mitocondrias/metabolismo , Mutación Missense , Enzima Bifuncional Peroxisomal/genética , Secuencia de Aminoácidos , Animales , Población Negra , Cromosomas Humanos Par 3 , Modelos Animales de Enfermedad , Síndrome de Fanconi/etnología , Femenino , Ligamiento Genético , Humanos , Masculino , Ratones , Ratones Noqueados , Datos de Secuencia Molecular , Linaje , Enzima Bifuncional Peroxisomal/química , Enzima Bifuncional Peroxisomal/metabolismo , Fenotipo , Análisis de Secuencia de ADNRESUMEN
A key link between amino acid catabolism and immune regulation in cancer is the augmented tryptophan (Trp) catabolism through the kynurenine pathway (KP), a metabolic route induced by interferon-γ (IFN-γ) and related to poor prognosis in melanomas. Besides its role in cancer, IFN-γ plays a key role in the control of pigmentation homeostasis. Here we measured KP metabolites in human melanoma lines and skin melanocytes and fibroblasts in response to IFN-γ. In general, IFN-γ affected KP in skin cells more than in melanoma cells, supporting IFN-γ roles in skin physiology and that of stromal cells in modulating the tumor microenvironment.
Asunto(s)
Interferón gamma/metabolismo , Quinurenina/biosíntesis , Melanocitos/metabolismo , Melanoma/metabolismo , Melanoma/patología , Línea Celular Tumoral , HumanosRESUMEN
After infection of B cells, Epstein-Barr virus (EBV) engages host pathways that mediate cell proliferation and transformation, contributing to the propensity of the virus to drive immune dysregulation and lymphomagenesis. We found that the EBV protein EBNA2 initiates nicotinamide adenine dinucleotide (NAD) de novo biosynthesis by driving expression of the metabolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1) in infected B cells. Virus-enforced NAD production sustained mitochondrial complex I activity, to match adenosine triphosphate (ATP) production with bioenergetic requirements of proliferation and transformation. In transplant patients, IDO1 expression in EBV-infected B cells, and a serum signature of increased IDO1 activity, preceded development of lymphoma. In humanized mice infected with EBV, IDO1 inhibition reduced both viremia and lymphomagenesis. Virus-orchestrated NAD biosynthesis is therefore a druggable metabolic vulnerability of EBV-driven B cell transformation, opening therapeutic possibilities for EBV-related diseases.
Asunto(s)
Adenosina Trifosfato , Linfocitos B , Transformación Celular Viral , Infecciones por Virus de Epstein-Barr , Antígenos Nucleares del Virus de Epstein-Barr , Herpesvirus Humano 4 , Indolamina-Pirrol 2,3,-Dioxigenasa , NAD , Animales , Humanos , Ratones , Adenosina Trifosfato/metabolismo , Linfocitos B/inmunología , Linfocitos B/metabolismo , Proliferación Celular , Complejo I de Transporte de Electrón/metabolismo , Infecciones por Virus de Epstein-Barr/virología , Antígenos Nucleares del Virus de Epstein-Barr/metabolismo , Herpesvirus Humano 4/fisiología , Indolamina-Pirrol 2,3,-Dioxigenasa/metabolismo , Indolamina-Pirrol 2,3,-Dioxigenasa/genética , Linfoma/virología , NAD/metabolismo , Proteínas Virales , ViremiaRESUMEN
Mitochondria are important regulators of macrophage polarisation. Here, we show that arginase-2 (Arg2) is a microRNA-155 (miR-155) and interleukin-10 (IL-10) regulated protein localized at the mitochondria in inflammatory macrophages, and is critical for IL-10-induced modulation of mitochondrial dynamics and oxidative respiration. Mechanistically, the catalytic activity and presence of Arg2 at the mitochondria is crucial for oxidative phosphorylation. We further show that Arg2 mediates this process by increasing the activity of complex II (succinate dehydrogenase). Moreover, Arg2 is essential for IL-10-mediated downregulation of the inflammatory mediators succinate, hypoxia inducible factor 1α (HIF-1α) and IL-1ß in vitro. Accordingly, HIF-1α and IL-1ß are highly expressed in an LPS-induced in vivo model of acute inflammation using Arg2-/- mice. These findings shed light on a new arm of IL-10-mediated metabolic regulation, working to resolve the inflammatory status of the cell.
Asunto(s)
Arginasa/metabolismo , Interleucina-10/metabolismo , Macrófagos/metabolismo , Mitocondrias/metabolismo , Animales , Arginasa/genética , Regulación hacia Abajo , Femenino , Interleucina-1beta/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados/genética , Mitocondrias/enzimología , Succinato Deshidrogenasa/metabolismoRESUMEN
Serum acetate increases upon systemic infection. Acutely, assimilation of acetate expands the capacity of memory CD8+ T cells to produce IFN-γ. Whether acetate modulates memory CD8+ T cell metabolism and function during pathogen re-encounter remains unexplored. Here we show that at sites of infection, high acetate concentrations are being reached, yet memory CD8+ T cells shut down the acetate assimilating enzymes ACSS1 and ACSS2. Acetate, being thus largely excluded from incorporation into cellular metabolic pathways, now had different effects, namely (1) directly activating glutaminase, thereby augmenting glutaminolysis, cellular respiration, and survival, and (2) suppressing TCR-triggered calcium flux, and consequently cell activation and effector cell function. In vivo, high acetate abundance at sites of infection improved pathogen clearance while reducing immunopathology. This indicates that, during different stages of the immune response, the same metabolite-acetate-induces distinct immunometabolic programs within the same cell type.
Asunto(s)
Acetatos/metabolismo , Antiinflamatorios/metabolismo , Linfocitos T CD8-positivos/metabolismo , Acetatos/sangre , Acetatos/inmunología , Animales , Antiinflamatorios/inmunología , Linfocitos T CD8-positivos/citología , Linfocitos T CD8-positivos/inmunología , Femenino , Humanos , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
Natural killer (NK) cells are lymphocytes with important anti-tumour functions. Cytokine activation of NK cell glycolysis and oxidative phosphorylation (OXPHOS) are essential for robust NK cell responses. However, the mechanisms leading to this metabolic phenotype are unclear. Here we show that the transcription factor cMyc is essential for IL-2/IL-12-induced metabolic and functional responses in mice. cMyc protein levels are acutely regulated by amino acids; cMyc protein is lost rapidly when glutamine is withdrawn or when system L-amino acid transport is blocked. We identify SLC7A5 as the predominant system L-amino acid transporter in activated NK cells. Unlike other lymphocyte subsets, glutaminolysis and the tricarboxylic acid cycle do not sustain OXPHOS in activated NK cells. Glutamine withdrawal, but not the inhibition of glutaminolysis, results in the loss of cMyc protein, reduced cell growth and impaired NK cell responses. These data identify an essential role for amino acid-controlled cMyc for NK cell metabolism and function.
Asunto(s)
Aminoácidos/química , Células Asesinas Naturales/citología , Proteínas Proto-Oncogénicas c-myc/metabolismo , Animales , Citocinas/metabolismo , Glutamina/química , Glucógeno Sintasa Quinasa 3/metabolismo , Glucólisis , Humanos , Células K562 , Células Asesinas Naturales/metabolismo , Transportador de Aminoácidos Neutros Grandes 1/metabolismo , Subgrupos Linfocitarios/metabolismo , Masculino , Diana Mecanicista del Complejo 1 de la Rapamicina/metabolismo , Ratones , Ratones Endogámicos C57BL , Fosforilación Oxidativa , Proteómica , Ácidos Tricarboxílicos/químicaRESUMEN
Immune cell metabolism is dynamically regulated in parallel with the substantial changes in cellular function that accompany immune cell activation. While these changes in metabolism are important for facilitating the increased energetic and biosynthetic demands of activated cells, immune cell metabolism also has direct roles in controlling the functions of immune cells and shaping the immune response. A theme is emerging wherein nutrients, metabolic enzymes, and metabolites can act as an extension of the established immune signal transduction pathways, thereby adding an extra layer of complexity to the regulation of immunity. This Review will outline the metabolic configurations adopted by different immune cell subsets, describe the emerging roles for metabolic enzymes and metabolites in the control of immune cell function, and discuss the therapeutic implications of this emerging immune regulatory axis.
Asunto(s)
Sistema Inmunológico/metabolismo , Adenosina Trifosfato/biosíntesis , Animales , Glucólisis , Humanos , Sistema Inmunológico/citología , Memoria Inmunológica , Infecciones/inmunología , Infecciones/metabolismo , Infecciones/terapia , Linfocitos/clasificación , Linfocitos/inmunología , Linfocitos/metabolismo , Modelos Inmunológicos , Neoplasias/inmunología , Neoplasias/metabolismo , Neoplasias/terapia , Fosforilación Oxidativa , Transducción de Señal/inmunología , Microambiente Tumoral/inmunología , Microambiente Tumoral/fisiologíaRESUMEN
We recently reported an autosomal dominant form of renal Fanconi syndrome caused by a missense mutation in the third codon of the peroxisomal protein EHHADH. The mutation mistargets EHHADH to mitochondria, thereby impairing mitochondrial energy production and, consequently, reabsorption of electrolytes and low-molecular-weight nutrients in the proximal tubule. Here, we further elucidate the molecular mechanism underlying this pathology. We find that mutated EHHADH is incorporated into mitochondrial trifunctional protein (MTP), thereby disturbing ß-oxidation of long-chain fatty acids. The resulting MTP deficiency leads to a characteristic accumulation of hydroxyacyl- and acylcarnitines. Mutated EHHADH also limits respiratory complex I and corresponding supercomplex formation, leading to decreases in oxidative phosphorylation capacity, mitochondrial membrane potential maintenance, and ATP generation. Activity of the Na(+)/K(+)-ATPase is thereby diminished, ultimately decreasing the transport activity of the proximal tubule cells.