RESUMEN
Growing evidence supports the importance of the p53 tumor suppressor in metabolism but the mechanisms underlying p53-mediated control of metabolism remain poorly understood. Here, we identify the multifunctional E4F1 protein as a key regulator of p53 metabolic functions in adipocytes. While E4F1 expression is upregulated during obesity, E4f1 inactivation in mouse adipose tissue results in a lean phenotype associated with insulin resistance and protection against induced obesity. Adipocytes lacking E4F1 activate a p53-dependent transcriptional program involved in lipid metabolism. The direct interaction between E4F1 and p53 and their co-recruitment to the Steaoryl-CoA Desaturase-1 locus play an important role to regulate monounsaturated fatty acids synthesis in adipocytes. Consistent with the role of this E4F1-p53-Steaoryl-CoA Desaturase-1 axis in adipocytes, p53 inactivation or diet complementation with oleate partly restore adiposity and improve insulin sensitivity in E4F1-deficient mice. Altogether, our findings identify a crosstalk between E4F1 and p53 in the control of lipid metabolism in adipocytes that is relevant to obesity and insulin resistance.
Asunto(s)
Adipocitos/metabolismo , Tejido Adiposo/metabolismo , Obesidad/genética , Proteínas Represoras/genética , Estearoil-CoA Desaturasa/genética , Proteína p53 Supresora de Tumor/genética , Ubiquitina-Proteína Ligasas/genética , Adipocitos/patología , Tejido Adiposo/patología , Adulto , Anciano , Animales , Índice de Masa Corporal , Ácidos Grasos Monoinsaturados/metabolismo , Femenino , Regulación de la Expresión Génica , Humanos , Resistencia a la Insulina , Metabolismo de los Lípidos/genética , Masculino , Ratones , Ratones Noqueados , Persona de Mediana Edad , Obesidad/metabolismo , Obesidad/patología , Proteínas Represoras/deficiencia , Proteínas Represoras/metabolismo , Transducción de Señal , Estearoil-CoA Desaturasa/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Ubiquitina-Proteína Ligasas/deficiencia , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
Well-differentiated and dedifferentiated liposarcomas (LPSs) are characterized by a systematic amplification of the MDM2 oncogene, which encodes a key negative regulator of the p53 pathway. The molecular mechanisms underlying MDM2 overexpression while sparing wild-type p53 in LPS remain poorly understood. Here, we show that the p53-independent metabolic functions of chromatin-bound MDM2 are exacerbated in LPS and mediate an addiction to serine metabolism that sustains nucleotide synthesis and tumor growth. Treatment of LPS cells with Nutlin-3A, a pharmacological inhibitor of the MDM2-p53 interaction, stabilized p53 but unexpectedly enhanced MDM2-mediated control of serine metabolism by increasing its recruitment to chromatin, likely explaining the poor clinical efficacy of this class of MDM2 inhibitors. In contrast, genetic or pharmacological inhibition of chromatin-bound MDM2 by SP141, a distinct MDM2 inhibitor triggering its degradation, or interfering with de novo serine synthesis, impaired LPS growth both in vitro and in clinically relevant patient-derived xenograft models. Our data indicate that targeting MDM2 functions in serine metabolism represents a potential therapeutic strategy for LPS.
Asunto(s)
Antineoplásicos , Liposarcoma , Antineoplásicos/uso terapéutico , Humanos , Liposarcoma/tratamiento farmacológico , Liposarcoma/genética , Proteínas Proto-Oncogénicas c-mdm2/metabolismo , Serina/uso terapéutico , Proteína p53 Supresora de Tumor/genéticaRESUMEN
Accumulating evidence indicates that the MDM2 oncoprotein promotes tumorigenesis beyond its canonical negative effects on the p53 tumor suppressor, but these p53-independent functions remain poorly understood. Here, we show that a fraction of endogenous MDM2 is actively imported in mitochondria to control respiration and mitochondrial dynamics independently of p53. Mitochondrial MDM2 represses the transcription of NADH-dehydrogenase 6 (MT-ND6) in vitro and in vivo, impinging on respiratory complex I activity and enhancing mitochondrial ROS production. Recruitment of MDM2 to mitochondria increases during oxidative stress and hypoxia. Accordingly, mice lacking MDM2 in skeletal muscles exhibit higher MT-ND6 levels, enhanced complex I activity, and increased muscular endurance in mild hypoxic conditions. Furthermore, increased mitochondrial MDM2 levels enhance the migratory and invasive properties of cancer cells. Collectively, these data uncover a previously unsuspected function of the MDM2 oncoprotein in mitochondria that play critical roles in skeletal muscle physiology and may contribute to tumor progression.
Asunto(s)
Carcinoma de Pulmón de Células no Pequeñas/patología , Transformación Celular Neoplásica/patología , Complejo I de Transporte de Electrón/metabolismo , Regulación Neoplásica de la Expresión Génica , Mitocondrias/patología , Proteínas Proto-Oncogénicas c-mdm2/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Adenocarcinoma/patología , Animales , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Movimiento Celular , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Complejo I de Transporte de Electrón/genética , Genoma Mitocondrial , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mitocondrias/genética , Mitocondrias/metabolismo , Invasividad Neoplásica , Estrés Oxidativo , Proteínas Proto-Oncogénicas c-mdm2/genética , Transducción de Señal , Transcripción Genética , Células Tumorales Cultivadas , Proteína p53 Supresora de Tumor/genética , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The multifunctional protein E4 transcription factor 1 (E4F1) is an essential regulator of epidermal stem cell (ESC) maintenance. Here, we found that E4F1 transcriptionally regulates a metabolic program involved in pyruvate metabolism that is required to maintain skin homeostasis. E4F1 deficiency in basal keratinocytes resulted in deregulated expression of dihydrolipoamide acetyltransferase (Dlat), a gene encoding the E2 subunit of the mitochondrial pyruvate dehydrogenase (PDH) complex. Accordingly, E4f1 knock-out (KO) keratinocytes exhibited impaired PDH activity and a redirection of the glycolytic flux toward lactate production. The metabolic reprogramming of E4f1 KO keratinocytes associated with remodeling of their microenvironment and alterations of the basement membrane, led to ESC mislocalization and exhaustion of the ESC pool. ShRNA-mediated depletion of Dlat in primary keratinocytes recapitulated defects observed upon E4f1 inactivation, including increased lactate secretion, enhanced activity of extracellular matrix remodeling enzymes, and impaired clonogenic potential. Altogether, our data reveal a central role for Dlat in the metabolic program regulated by E4F1 in basal keratinocytes and illustrate the importance of PDH activity in skin homeostasis.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Acetiltransferasa de Residuos Dihidrolipoil-Lisina/metabolismo , Homeostasis , Proteínas Mitocondriales/metabolismo , Piel/metabolismo , Factores de Transcripción/metabolismo , Animales , Animales Recién Nacidos , Membrana Basal/metabolismo , Adhesión Celular , Células Cultivadas , Microambiente Celular , Proteínas de Unión al ADN/deficiencia , Acetiltransferasa de Residuos Dihidrolipoil-Lisina/genética , Células Epidérmicas , Epidermis/metabolismo , Regulación de la Expresión Génica , Queratinocitos/citología , Queratinocitos/metabolismo , Ratones Noqueados , Proteínas Mitocondriales/genética , Transportadores de Ácidos Monocarboxílicos/metabolismo , Proteínas Musculares/metabolismo , Piruvatos/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Proteínas Represoras , Células Madre/metabolismo , Factores de Transcripción/deficiencia , Ubiquitina-Proteína LigasasRESUMEN
The mitochondrial pyruvate dehydrogenase (PDH) complex (PDC) acts as a central metabolic node that mediates pyruvate oxidation and fuels the tricarboxylic acid cycle to meet energy demand. Here, we reveal another level of regulation of the pyruvate oxidation pathway in mammals implicating the E4 transcription factor 1 (E4F1). E4F1 controls a set of four genes [dihydrolipoamide acetlytransferase (Dlat), dihydrolipoyl dehydrogenase (Dld), mitochondrial pyruvate carrier 1 (Mpc1), and solute carrier family 25 member 19 (Slc25a19)] involved in pyruvate oxidation and reported to be individually mutated in human metabolic syndromes. E4F1 dysfunction results in 80% decrease of PDH activity and alterations of pyruvate metabolism. Genetic inactivation of murine E4f1 in striated muscles results in viable animals that show low muscle PDH activity, severe endurance defects, and chronic lactic acidemia, recapitulating some clinical symptoms described in PDC-deficient patients. These phenotypes were attenuated by pharmacological stimulation of PDH or by a ketogenic diet, two treatments used for PDH deficiencies. Taken together, these data identify E4F1 as a master regulator of the PDC.