RESUMEN
The hexosamine biosynthetic pathway (HBP) generates uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) for glycan synthesis and O-linked GlcNAc (O-GlcNAc) protein modifications. Despite the established role of the HBP in metabolism and multiple diseases, regulation of the HBP remains largely undefined. Here, we show that spliced X-box binding protein 1 (Xbp1s), the most conserved signal transducer of the unfolded protein response (UPR), is a direct transcriptional activator of the HBP. We demonstrate that the UPR triggers HBP activation via Xbp1s-dependent transcription of genes coding for key, rate-limiting enzymes. We further establish that this previously unrecognized UPR-HBP axis is triggered in a variety of stress conditions. Finally, we demonstrate a physiologic role for the UPR-HBP axis by showing that acute stimulation of Xbp1s in heart by ischemia/reperfusion confers robust cardioprotection in part through induction of the HBP. Collectively, these studies reveal that Xbp1s couples the UPR to the HBP to protect cells under stress.
Asunto(s)
Vías Biosintéticas , Proteínas de Unión al ADN/metabolismo , Hexosaminas/metabolismo , Factores de Transcripción/metabolismo , Respuesta de Proteína Desplegada , Animales , Glutamina-Fructosa-6-Fosfato Transaminasa (Isomerizadora) , Humanos , Masculino , Ratones , Ratones Transgénicos , Isquemia Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/metabolismo , Miocitos Cardíacos/metabolismo , Transferasas de Grupos Nitrogenados/genética , Factores de Transcripción del Factor Regulador X , Proteína 1 de Unión a la X-BoxRESUMEN
[Figure: see text].
Asunto(s)
Autofagia , Beclina-1/farmacología , Daño por Reperfusión Miocárdica/metabolismo , Miocitos Cardíacos/metabolismo , Animales , Proteína 7 Relacionada con la Autofagia/genética , Proteína 7 Relacionada con la Autofagia/metabolismo , Beclina-1/uso terapéutico , Células Cultivadas , Ratones , Ratones Endogámicos C57BL , Contracción Miocárdica , Daño por Reperfusión Miocárdica/tratamiento farmacológico , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/fisiología , Ratas , Ratas Sprague-Dawley , Especies Reactivas de Oxígeno/metabolismo , Proteínas Recombinantes/farmacología , Proteínas Recombinantes/uso terapéuticoRESUMEN
Increasing non-shivering thermogenesis (NST), which expends calories as heat rather than storing them as fat, is championed as an effective way to combat obesity and metabolic disease. Innate mechanisms constraining the capacity for NST present a fundamental limitation to this approach, yet are not well understood. Here, we provide evidence that Regulator of Calcineurin 1 (RCAN1), a feedback inhibitor of the calcium-activated protein phosphatase calcineurin (CN), acts to suppress two distinctly different mechanisms of non-shivering thermogenesis (NST): one involving the activation of UCP1 expression in white adipose tissue, the other mediated by sarcolipin (SLN) in skeletal muscle. UCP1 generates heat at the expense of reducing ATP production, whereas SLN increases ATP consumption to generate heat. Gene expression profiles demonstrate a high correlation between Rcan1 expression and metabolic syndrome. On an evolutionary timescale, in the context of limited food resources, systemic suppression of prolonged NST by RCAN1 might have been beneficial; however, in the face of caloric abundance, RCAN1-mediated suppression of these adaptive avenues of energy expenditure may now contribute to the growing epidemic of obesity.
Asunto(s)
Péptidos y Proteínas de Señalización Intracelular/metabolismo , Metabolismo , Proteínas Musculares/metabolismo , Termogénesis , Células 3T3-L1 , Adipocitos/citología , Adipocitos/efectos de los fármacos , Adipocitos/metabolismo , Tejido Adiposo/metabolismo , Tejido Adiposo Beige/efectos de los fármacos , Tejido Adiposo Beige/metabolismo , Tejido Adiposo Blanco/efectos de los fármacos , Tejido Adiposo Blanco/metabolismo , Adrenérgicos/farmacología , Animales , Calcineurina/metabolismo , Proteínas de Unión al Calcio , Diferenciación Celular/efectos de los fármacos , Frío , Femenino , Resistencia a la Insulina , Péptidos y Proteínas de Señalización Intracelular/deficiencia , Metabolismo de los Lípidos/efectos de los fármacos , Hígado/metabolismo , Masculino , Síndrome Metabólico/metabolismo , Metabolismo/efectos de los fármacos , Ratones , Ratones Noqueados , Proteínas Musculares/deficiencia , Proteínas Musculares/genética , Músculo Esquelético/metabolismo , Músculo Estriado/metabolismo , Obesidad/metabolismo , Obesidad/patología , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/metabolismo , Regiones Promotoras Genéticas/genética , Proteolípidos/genética , Proteolípidos/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Termogénesis/efectos de los fármacos , Proteína Desacopladora 1/metabolismoRESUMEN
BACKGROUND: L-type calcium channel activity is critical to afterload-induced hypertrophic growth of the heart. However, the mechanisms governing mechanical stress-induced activation of L-type calcium channel activity are obscure. Polycystin-1 (PC-1) is a G protein-coupled receptor-like protein that functions as a mechanosensor in a variety of cell types and is present in cardiomyocytes. METHODS AND RESULTS: We subjected neonatal rat ventricular myocytes to mechanical stretch by exposing them to hypo-osmotic medium or cyclic mechanical stretch, triggering cell growth in a manner dependent on L-type calcium channel activity. RNAi-dependent knockdown of PC-1 blocked this hypertrophy. Overexpression of a C-terminal fragment of PC-1 was sufficient to trigger neonatal rat ventricular myocyte hypertrophy. Exposing neonatal rat ventricular myocytes to hypo-osmotic medium resulted in an increase in α1C protein levels, a response that was prevented by PC-1 knockdown. MG132, a proteasomal inhibitor, rescued PC-1 knockdown-dependent declines in α1C protein. To test this in vivo, we engineered mice harboring conditional silencing of PC-1 selectively in cardiomyocytes (PC-1 knockout) and subjected them to mechanical stress in vivo (transverse aortic constriction). At baseline, PC-1 knockout mice manifested decreased cardiac function relative to littermate controls, and α1C L-type calcium channel protein levels were significantly lower in PC-1 knockout hearts. Whereas control mice manifested robust transverse aortic constriction-induced increases in cardiac mass, PC-1 knockout mice showed no significant growth. Likewise, transverse aortic constriction-elicited increases in hypertrophic markers and interstitial fibrosis were blunted in the knockout animals CONCLUSION: PC-1 is a cardiomyocyte mechanosensor that is required for cardiac hypertrophy through a mechanism that involves stabilization of α1C protein.
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Canales de Calcio Tipo L/fisiología , Cardiomegalia/etiología , Mecanotransducción Celular/fisiología , Miocitos Cardíacos/fisiología , Canales Catiónicos TRPP/fisiología , Animales , Animales Recién Nacidos , Biomarcadores , Canales de Calcio Tipo L/biosíntesis , Canales de Calcio Tipo L/genética , Cardiomegalia/prevención & control , Células Cultivadas , Fibrosis , Hipertrofia , Soluciones Hipotónicas/farmacología , Masculino , Ratones , Ratones Noqueados , Miocitos Cardíacos/efectos de los fármacos , Mapeo de Interacción de Proteínas , Estabilidad Proteica , Estructura Terciaria de Proteína , Interferencia de ARN , Ratas , Ratas Sprague-Dawley , Proteínas Recombinantes de Fusión/metabolismo , Estrés Mecánico , Canales Catiónicos TRPP/química , Canales Catiónicos TRPP/genéticaRESUMEN
PURPOSE OF REVIEW: This article provides an overview, highlighting recent findings, of a major mechanism of gene regulation and its relevance to the pathophysiology of heart failure. RECENT FINDINGS: The syndrome of heart failure is a complex and highly prevalent condition, one in which the heart undergoes substantial structural remodeling. Triggered by a wide range of disease-related cues, heart failure pathophysiology is governed by both genetic and epigenetic events. Epigenetic mechanisms, such as chromatin/DNA modifications and noncoding RNAs, have emerged as molecular transducers of environmental stimuli to control gene expression. Here, we emphasize metabolic milieu, aging, and hemodynamic stress as they impact the epigenetic landscape of the myocardium. SUMMARY: Recent studies in multiple fields, including cancer, stem cells, development, and cardiovascular biology, have uncovered biochemical ties linking epigenetic machinery and cellular energetics and mitochondrial function. Elucidation of these connections will afford molecular insights into long-established epidemiological observations. With time, exploitation of the epigenetic machinery therapeutically may emerge with clinical relevance.
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ADN Mitocondrial/metabolismo , Epigénesis Genética , Insuficiencia Cardíaca/etiología , Acetilación , Animales , Cromatina/metabolismo , Metilación de ADN , Humanos , ARN no TraducidoRESUMEN
Histone deacetylases (HDACs) regulate cardiac plasticity; however, their molecular targets are unknown. As autophagy contributes to pathological cardiac remodeling, we hypothesized that HDAC inhibitors target autophagy. The prototypical HDAC inhibitor (HDACi), trichostatin A (TSA), attenuated both load- and agonist-induced hypertrophic growth and abolished the associated activation of autophagy. Phenylephrine (PE)-triggered hypertrophy and autophagy in cultured cardiomyocytes were each blocked by a panel of structurally distinct HDAC inhibitors. RNAi-mediated knockdown of either Atg5 or Beclin 1, two essential autophagy effectors, was similarly capable of suppressing ligand-induced autophagy and myocyte growth. RNAi experiments uncovered the class I isoforms HDAC1 and HDAC2 as required for the autophagic response. To test the functional requirement of autophagic activation, we studied mice that overexpress Beclin 1 in cardiomyocytes. In these animals with a fourfold amplified autophagic response to TAC, TSA abolished TAC-induced increases in autophagy and blunted load-induced hypertrophy. Finally, we subjected animals with preexisting hypertrophy to HDACi, finding that ventricular mass reverted to near-normal levels and ventricular function normalized completely. Together, these data implicate autophagy as an obligatory element in pathological cardiac remodeling and point to HDAC1/2 as required effectors. Also, these data reveal autophagy as a previously unknown target of HDAC inhibitor therapy.
Asunto(s)
Autofagia/efectos de los fármacos , Cardiomegalia/prevención & control , Inhibidores de Histona Desacetilasas/farmacología , Acetilación , Animales , Cardiomegalia/inducido químicamente , Cardiomegalia/inmunología , Fenilefrina/farmacología , Ratas , Ratas Sprague-DawleyRESUMEN
NADPH oxidase isoform-2 (NOX2) generates reactive oxygen species (ROS) that contribute to neurodegenerative and cardiovascular pathologies. However, validation of NOX2 as a pharmacotherapeutic target has been hampered by a lack of mechanistically-defined inhibitors. Using cellular and biochemical assays, we explored previously reported inhibitors of ROS production (perhexiline, suramin, VAS2870 and two Shionogi patent compounds) as direct NOX2 inhibitors. All but suramin, which presumably lacks cell penetrance, inhibit cellular ROS production. However, only perhexiline and suramin inhibit biochemical NOX2 activity. Indeed, our data suggest that NOX2 inhibition by perhexiline may contribute significantly to its demonstrated cardioprotective effects. Inhibition of protein kinase CßII explains the cellular activity of the Shionogi compounds, whereas VAS2870 inhibits by an as-yet unidentified mechanism unrelated to direct NOX2 function or subunit assembly. These data delineate the mechanisms of action of these compounds and highlight their strengths and limitations for use in future target validation studies.
Asunto(s)
Inhibidores Enzimáticos/farmacología , Glicoproteínas de Membrana/antagonistas & inhibidores , NADPH Oxidasas/antagonistas & inhibidores , Especies Reactivas de Oxígeno/metabolismo , Secuencia de Bases , Benzoxazoles/farmacología , Fármacos Cardiovasculares/farmacología , Células Cultivadas , Humanos , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Datos de Secuencia Molecular , NADPH Oxidasa 2 , NADPH Oxidasas/genética , NADPH Oxidasas/metabolismo , Neutrófilos/efectos de los fármacos , Neutrófilos/enzimología , Neutrófilos/metabolismo , Perhexilina/farmacología , Proteína Quinasa C/antagonistas & inhibidores , Proteína Quinasa C beta , Especies Reactivas de Oxígeno/antagonistas & inhibidores , Suramina/farmacología , Triazoles/farmacologíaRESUMEN
PURPOSE OF REVIEW: Despite maximum medical and mechanical support therapy, heart failure remains a relentlessly progressive disorder with substantial morbidity and mortality. Autophagy, an evolutionarily conserved process of cellular cannibalization, has been implicated in virtually all forms of cardiovascular disease. Indeed, its role is context dependent, antagonizing or promoting disease depending on the circumstance. Here, we review current understanding of the role of autophagy in the pathogenesis of heart failure and explore this pathway as a target of therapeutic intervention. RECENT FINDINGS: In preclinical models of heart disease, cardiomyocyte autophagic flux is activated; indeed, its role in disease pathogenesis is the subject of intense investigation to define mechanism. Similarly, in failing human heart of a variety of etiologies, cardiomyocyte autophagic activity is upregulated, and therapy, such as with mechanical support systems, elicits declines in autophagy activity. However, when suppression of autophagy is complete, rapid and catastrophic cell death occurs, consistent with a model in which basal autophagic flux is required for proteostasis. Thus, a narrow zone of 'optimal' autophagy seems to exist. The challenge moving forward is to tune the stress-triggered autophagic response within that 'sweet spot' range for therapeutic benefit. SUMMARY: Whereas we have known for some years of the participation of lysosomal mechanisms in heart disease, it is only recently that upstream mechanisms (autophagy) are being explored. The challenge for the future is to dissect the underlying circuitry and titrate the response into an optimal, proteostasis-promoting range in hopes of mitigating the ever-expanding epidemic of heart failure.
Asunto(s)
Autofagia , Insuficiencia Cardíaca/tratamiento farmacológico , Miocitos Cardíacos , Cardiomegalia , Enfermedad por Depósito de Glucógeno de Tipo IIb/fisiopatología , Insuficiencia Cardíaca/etiología , Humanos , Transducción de SeñalRESUMEN
Altering chromatin structure through histone posttranslational modifications has emerged as a key driver of transcriptional responses in cells. Modulation of these transcriptional responses by pharmacological inhibition of class I histone deacetylases (HDACs), a group of chromatin remodeling enzymes, has been successful in blocking the growth of some cancer cell types. These inhibitors also attenuate the pathogenesis of pathological cardiac remodeling by blunting and even reversing pathological hypertrophy. The mechanistic target of rapamycin (mTOR) is a critical sensor and regulator of cell growth that, as part of mTOR complex 1 (mTORC1), drives changes in protein synthesis and metabolism in both pathological and physiological hypertrophy. We demonstrated through pharmacological and genetic methods that inhibition of class I HDACs suppressed pathological cardiac hypertrophy through inhibition of mTOR activity. Mice genetically silenced for HDAC1 and HDAC2 had a reduced hypertrophic response to thoracic aortic constriction (TAC) and showed reduced mTOR activity. We determined that the abundance of tuberous sclerosis complex 2 (TSC2), an mTOR inhibitor, was increased through a transcriptional mechanism in cardiomyocytes when class I HDACs were inhibited. In neonatal rat cardiomyocytes, loss of TSC2 abolished HDAC-dependent inhibition of mTOR activity, and increased expression of TSC2 was sufficient to reduce hypertrophy in response to phenylephrine. These findings point to mTOR and TSC2-dependent control of mTOR as critical components of the mechanism by which HDAC inhibitors blunt pathological cardiac growth. These results also suggest a strategy to modulate mTOR activity and facilitate the translational exploitation of HDAC inhibitors in heart disease.
Asunto(s)
Cardiomegalia/metabolismo , Histona Desacetilasa 1/metabolismo , Histona Desacetilasa 2/metabolismo , Serina-Treonina Quinasas TOR/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Animales , Animales Recién Nacidos , Western Blotting , Cardiomegalia/genética , Línea Celular , Células Cultivadas , Histona Desacetilasa 1/genética , Histona Desacetilasa 2/genética , Inhibidores de Histona Desacetilasas/farmacología , Humanos , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/metabolismo , Péptidos Cíclicos/farmacología , Interferencia de ARN , Ratas Sprague-Dawley , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/efectos de los fármacos , Serina-Treonina Quinasas TOR/genética , Proteína 2 del Complejo de la Esclerosis Tuberosa , Proteínas Supresoras de Tumor/genéticaRESUMEN
SIGNIFICANCE: Autophagy is an evolutionarily ancient process of intracellular protein and organelle recycling required to maintain cellular homeostasis in the face of a wide variety of stresses. Dysregulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) leads to oxidative damage. Both autophagy and ROS/RNS serve pathological or adaptive roles within cardiomyocytes, depending on the context. RECENT ADVANCES: ROS/RNS and autophagy communicate with each other via both transcriptional and post-translational events. This cross talk, in turn, regulates the structural integrity of cardiomyocytes, promotes proteostasis, and reduces inflammation, events critical to disease pathogenesis. CRITICAL ISSUES: Dysregulation of either autophagy or redox state has been implicated in many cardiovascular diseases. Cardiomyocytes are rich in mitochondria, which make them particularly sensitive to oxidative damage. Maintenance of mitochondrial homeostasis and elimination of defective mitochondria are each critical to the maintenance of redox homeostasis. FUTURE DIRECTIONS: The complex interplay between autophagy and oxidative stress underlies a wide range of physiological and pathological events and its elucidation holds promise of potential clinical applicability.