RESUMEN
The response to osmotic stress is a highly conserved process for adapting to changing environmental conditions. Prior studies have shown that hyperosmolarity by addition of sorbitol to the growth medium is sufficient to increase both chronological and replicative lifespan in the budding yeast, Saccharomyces cerevisiae. Here we report a similar phenomenon in the nematode Caenorhabditis elegans. Addition of sorbitol to the nematode growth medium induces an adaptive osmotic response and increases C. elegans lifespan by about 35%. Lifespan extension from 5% sorbitol behaves similarly to dietary restriction in a variety of genetic backgrounds, increasing lifespan additively with mutation of daf-2(e1370) and independently of daf-16(mu86), sir-2.1(ok434), aak-2(ok524), and hif-1(ia04). Dietary restriction by bacterial deprivation or mutation of eat-2(ad1113) fails to further extend lifespan in the presence of 5% sorbitol. Two mutants with constitutive activation of the osmotic response, osm-5(p813) and osm-7(n1515), were found to be long-lived, and lifespan extension from sorbitol required the glycerol biosynthetic enzymes GPDH-1 and GPDH-2. Taken together, these observations demonstrate that exposure to sorbitol at levels sufficient to induce an adaptive osmotic response extends lifespan in worms and define the osmotic stress response pathway as a longevity pathway conserved between yeast and nematodes.
RESUMEN
The anticonvulsant ethosuximide has been previously shown to increase life span and promote healthspan in the nematode Caenorhabditis elegans at millimolar concentrations. Here we report that following exposure to ultraviolet irradiation at 254 nm, ethosuximide is converted into a compound that displays toxicity toward C. elegans. This effect is specific for ethosuximide, as the structurally related compounds trimethadione and succinimide do not show similar toxicities following UV exposure. Killing by UV-irradiated ethosuximide is not attenuated in chemosensory mutants that are resistant to toxicity associated with high doses of non-irradiated ethosuximide. Non-irradiated ethosuximide extends life span at 15°C or 20°C, but not at 25°C, while irradiated ethosuximide shows similar toxicity at all three temperatures. Dietary restriction by bacterial deprivation does not protect against toxicity from irradiated ethosuximide, while non-irradiated ethosuximide further extends the long life spans of restricted animals. These data support the model that ethosuximide extends life span by a mechanism that is, at least partially, distinct from dietary restriction by bacterial deprivation and demonstrates an unexpected photochemical conversion of ethosuximide into a toxic compound by UV light.
Asunto(s)
Anticonvulsivantes/efectos adversos , Caenorhabditis elegans/metabolismo , Etosuximida/efectos adversos , Longevidad/efectos de los fármacos , Longevidad/efectos de la radiación , Rayos Ultravioleta/efectos adversos , Animales , Anticonvulsivantes/farmacología , Etosuximida/farmacología , Privación de AlimentosRESUMEN
Appropriate regulation of mRNA translation is essential for growth and survival and the pathways that regulate mRNA translation have been highly conserved throughout eukaryotic evolution. Translation is controlled by a complex set of mechanisms acting at multiple levels, ranging from global protein synthesis to individual mRNAs. Recently, several mutations that perturb regulation of mRNA translation have also been found to increase longevity in three model organisms: the buddingyeast Saccharomyces cerevisiae, the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Many of these translation control factors can be mapped to a single pathway downstream of the nutrient responsive target of rapamycin (TOR) kinase. In this chapter, we will review the data suggesting that mRNA translation is an evolutionarily conserved modifier of longevity and discuss potential mechanisms by which mRNA translation could influence aging and age-associated disease in different species.
Asunto(s)
Regulación de la Expresión Génica , Longevidad/genética , Procesamiento Postranscripcional del ARN , ARN Mensajero/genética , Animales , Secuencia Conservada , Humanos , Biosíntesis de ProteínasRESUMEN
Studies in a variety of model organisms indicate that nutrient signaling is tightly coupled to longevity. In nutrient replete conditions, organisms develop, grow, and age quickly. When nutrients become sparse as with dietary restriction, growth and development decline, stress response pathways become induced and organisms live longer. Considerable effort has been devoted to understanding the molecular events mediating lifespan extension by dietary restriction. One central focus has been on nutrient-responsive signal transduction pathways including insulin/IGF-1, AMP kinase, protein kinase A and the TOR pathway. Here we describe the increasingly prominent links between TOR signaling and aging in invertebrates. Longevity studies in mammals are not published to date. Instead, we highlight studies in mouse models, which indicate that dampening the TOR pathway leads to widespread protection from an array of age-related diseases.
Asunto(s)
Envejecimiento/metabolismo , Proteínas Quinasas/metabolismo , Transducción de Señal , Envejecimiento/genética , Animales , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Humanos , Ratones , Modelos Biológicos , Neoplasias/genética , Neoplasias/metabolismo , Fosfatidilinositol 3-Quinasas/genética , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Quinasas/genética , Serina-Treonina Quinasas TORRESUMEN
The Caenorhabditis elegans von Hippel-Lindau tumor suppressor homolog VHL-1 is a cullin E3 ubiquitin ligase that negatively regulates the hypoxic response by promoting ubiquitination and degradation of the hypoxic response transcription factor HIF-1. Here, we report that loss of VHL-1 significantly increased life span and enhanced resistance to polyglutamine and beta-amyloid toxicity. Deletion of HIF-1 was epistatic to VHL-1, indicating that HIF-1 acts downstream of VHL-1 to modulate aging and proteotoxicity. VHL-1 and HIF-1 control longevity by a mechanism distinct from both dietary restriction and insulin-like signaling. These findings define VHL-1 and the hypoxic response as an alternative longevity and protein homeostasis pathway.
Asunto(s)
Envejecimiento/fisiología , Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/fisiología , Proteínas Cullin/metabolismo , Oxígeno/fisiología , Complejo de la Endopetidasa Proteasomal/metabolismo , Factores de Transcripción/metabolismo , Péptidos beta-Amiloides/toxicidad , Animales , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Restricción Calórica , Proteínas Cullin/genética , Femenino , Fertilidad , Regulación de la Expresión Génica , Homeostasis , Insulina/metabolismo , Longevidad/fisiología , Masculino , Modelos Animales , Péptidos/toxicidad , Interferencia de ARN , Receptor de Insulina/genética , Receptor de Insulina/metabolismo , Transducción de Señal , Factores de Transcripción/genética , UbiquitinaciónRESUMEN
Genetic economy leads to symmetric distributions of chemically identical subunits in icosaherdal and helical viruses. Modification of the subunit genes of a variety of viruses has permitted the display of polypeptides on both the infectious virions and virus particles made in expression systems. Icosahedral chimeric particles of this type often display novel properties resulting in high local concentrations of the insert. Here we report an extension of this concept in which entire proteins were chemically cross-linked to lysine and cysteine residues genetically engineered on the coat protein of icosahedral Cowpea mosaic virus particles. Three exogenous proteins, the LRR domain of internalin B, the T4 lysozyme, and the Intron 8 gene product of the of the HER2 tyrosine kinase receptor were derivatized with appropriate bifunctional cross-linkers and conjugated to the virus capsid. Characterization of these particles demonstrated that (1) virtually 100% occupancy of the 60 sites was achieved; (2) biological activity (either enzyme or binding specificity) of the attached protein was preserved; (3) in one case (LRR-internalin B) the attached protein conformed with the icosahedral symmetry to the extent that a reconstruction of the derivatized particles displayed added density with a shape consistent with the X-ray structure of the attached protein. Strategies demonstrated here allow virus particle targeting to specific cell types and the use of an icosahedral virus as a platform for structure determination of small proteins at moderate resolution.
Asunto(s)
Comovirus/química , Proteínas/análisis , Proteínas/química , Proteínas Bacterianas , Bacteriófago T4/enzimología , Proteínas de la Cápside/química , Proteínas de la Cápside/genética , Cromatografía Liquida , Comovirus/genética , Comovirus/aislamiento & purificación , Reactivos de Enlaces Cruzados/química , Sistemas de Liberación de Medicamentos , Proteínas de la Membrana/química , Modelos Moleculares , Estructura Molecular , Muramidasa/química , Ingeniería de Proteínas , Estructura Terciaria de Proteína , Receptor ErbB-2/químicaRESUMEN
Retention of intron 8 in alternative HER-2 mRNA generates an inhibitory secreted ligand, Herstatin, with a novel receptor-binding domain (RBD) encoded by the intron. This study examines binding interactions with several receptors and investigates sequence variations in intron 8. The RBD, expressed as a peptide, binds at nM concentrations to HER-2, the EGFR, DeltaEGFR, HER-4 and to the IGF-1 receptor, but not to HER-3 nor to the FGF-3 receptor, whereas a rare mutation in the RBD (Arg to Ile) eliminates receptor binding. The full-length Herstatin binds with 3-4-fold higher affinity than its RBD, but with approximately 10-fold lower affinity to the IGF-IR. Sequence conservation in rhesus monkey but not in rat suggests that intron 8 recently diverged as a receptor-binding module critical for the function of Herstatin.