RESUMO
The mechanistic basis for the biogenesis of peptide hormones and growth factors is poorly understood. Here, we show that the conserved endoplasmic reticulum membrane translocon-associated protein α (TRAPα), also known as signal sequence receptor 1, plays a critical role in the biosynthesis of insulin. Genetic analysis in the nematode Caenorhabditis elegans and biochemical studies in pancreatic ß cells reveal that TRAPα deletion impairs preproinsulin translocation while unexpectedly disrupting distal steps in insulin biogenesis including proinsulin processing and secretion. The association of common intronic single-nucleotide variants in the human TRAPα gene with susceptibility to type 2 diabetes and pancreatic ß cell dysfunction suggests that impairment of preproinsulin translocation and proinsulin trafficking may contribute to the pathogenesis of type 2 diabetes.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/metabolismo , Proteínas de Ligação ao Cálcio/metabolismo , Insulina/biossíntese , Glicoproteínas de Membrana/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores de Peptídeos/metabolismo , Animais , Estresse do Retículo Endoplasmático , Insulina/metabolismo , Secreção de Insulina , Precursores de Proteínas/metabolismo , Proteínas Recombinantes de Fusão/metabolismoRESUMO
A feature common to late onset proteinopathic disorders is an accumulation of toxic protein conformers and aggregates in affected tissues. In the search for potential drug targets, many studies used high-throughput screens to find genes that modify the cytotoxicity of misfolded proteins. A complement to this approach is to focus on strategies that use protein aggregation as a phenotypic readout to identify pathways that control aggregate formation and maintenance. Here we use natural variation between strains of budding yeast to genetically map loci that influence the aggregation of a polyglutamine-containing protein derived from a mutant form of huntingtin, the causative agent in Huntington disease. Linkage analysis of progeny derived from a cross between wild and laboratory yeast strains revealed two polymorphic loci that modify polyglutamine aggregation. One locus contains the gene RFU1 which modifies ubiquitination states of misfolded proteins targeted by the E3-ubiquitin ligase complex Rsp5 Activity of the Rsp5 complex, and the mammalian homolog NEDD4, are critical in maintaining protein homeostasis in response to proteomic stress. Our analysis also showed linkage of the aggregation phenotype to a distinct locus containing a gene encoding the Rsp5-interacting Bul2 protein. Allele-swap experiments validated the impact of both RFU1 and BUL2 on huntingtin aggregation. Furthermore, we found that the nematode Caenorhabditis elegans' ortholog of Rsp5, wwp-1, also negatively regulates polyglutamine aggregation. Knockdown of the NEDD4 in human cells likewise altered polyglutamine aggregation. Taken together, these results implicate conserved processes involving the ubiquitin regulation network that modify protein aggregation and provide novel therapeutic targets for polyglutamine and other protein folding diseases.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas de Caenorhabditis elegans/genética , Ubiquitina-Proteína Ligases Nedd4/genética , Peptídeos/fisiologia , Proteínas de Saccharomyces cerevisiae/genética , Ubiquitina-Proteína Ligases/genética , Animais , Caenorhabditis elegans , Variação Genética , Células HEK293 , Humanos , Mutação , Saccharomycetales/fisiologiaRESUMO
Limiting the debilitating consequences of ageing is a major medical challenge of our time. Robust pharmacological interventions that promote healthy ageing across diverse genetic backgrounds may engage conserved longevity pathways. Here we report results from the Caenorhabditis Intervention Testing Program in assessing longevity variation across 22 Caenorhabditis strains spanning 3 species, using multiple replicates collected across three independent laboratories. Reproducibility between test sites is high, whereas individual trial reproducibility is relatively low. Of ten pro-longevity chemicals tested, six significantly extend lifespan in at least one strain. Three reported dietary restriction mimetics are mainly effective across C. elegans strains, indicating species and strain-specific responses. In contrast, the amyloid dye ThioflavinT is both potent and robust across the strains. Our results highlight promising pharmacological leads and demonstrate the importance of assessing lifespans of discrete cohorts across repeat studies to capture biological variation in the search for reproducible ageing interventions.
Assuntos
Caenorhabditis/efeitos dos fármacos , Patrimônio Genético , Longevidade/efeitos dos fármacos , Compostos Orgânicos/farmacologia , Animais , Benzotiazóis , Caenorhabditis/classificação , Caenorhabditis/genética , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/genética , Relação Dose-Resposta a Droga , Fertilidade/efeitos dos fármacos , Fertilidade/genética , Longevidade/genética , Reprodutibilidade dos Testes , Especificidade da Espécie , Tiazóis/farmacologiaRESUMO
Animals change developmental fates in response to external cues. In the nematode Caenorhabditis elegans, unfavorable environmental conditions induce a state of diapause known as dauer by inhibiting the conserved DAF-2 insulin-like signaling (ILS) pathway through incompletely understood mechanisms. We have previously established a role for the C. elegans dosage compensation protein DPY-21 in the control of dauer arrest and DAF-2 ILS. Here, we show that the histone H4 lysine 20 methyltransferase SET-4, which also influences dosage compensation, promotes dauer arrest in part by repressing the X-linked ins-9 gene, which encodes a new agonist insulin-like peptide (ILP) expressed specifically in the paired ASI sensory neurons that are required for dauer bypass. ins-9 repression in dauer-constitutive mutants requires DPY-21, SET-4 and the FoxO transcription factor DAF-16, which is the main target of DAF-2 ILS. By contrast, autosomal genes encoding major agonist ILPs that promote reproductive development are not repressed by DPY-21, SET-4 or DAF-16/FoxO. Our results implicate SET-4 as a sensory rheostat that reinforces developmental fates in response to environmental cues by modulating autocrine and paracrine DAF-2 ILS.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/enzimologia , Caenorhabditis elegans/crescimento & desenvolvimento , Meio Ambiente , Histona-Lisina N-Metiltransferase/metabolismo , Histonas/metabolismo , Lisina/metabolismo , Plasticidade Neuronal , Células Receptoras Sensoriais/fisiologia , Animais , Caenorhabditis elegans/genética , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Genes Ligados ao Cromossomo X , Larva/metabolismo , Masculino , Modelos Biológicos , Mutação/genética , Caracteres Sexuais , Transcriptoma/genéticaRESUMO
Vitamin D has multiple roles, including the regulation of bone and calcium homeostasis. Deficiency of 25-hydroxyvitamin D, the major circulating form of vitamin D, is associated with an increased risk of age-related chronic diseases, including Alzheimer's disease, Parkinson's disease, cognitive impairment, and cancer. In this study, we utilized Caenorhabditis elegans to examine the mechanism by which vitamin D influences aging. We found that vitamin-D3-induced lifespan extension requires the stress response pathway genes skn-1, ire-1, and xbp-1. Vitamin D3 (D3) induced expression of SKN-1 target genes but not canonical targets of XBP-1. D3 suppressed an important molecular pathology of aging, that of widespread protein insolubility, and prevented toxicity caused by human ß-amyloid. Our observation that D3 improves protein homeostasis and slows aging highlights the importance of maintaining appropriate vitamin D serum levels and may explain why such a wide variety of human age-related diseases are associated with vitamin D deficiency.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/genética , Proteínas de Transporte/genética , Proteínas de Ligação a DNA/genética , Homeostase/efeitos dos fármacos , Longevidade/fisiologia , Proteínas Serina-Treonina Quinases/genética , Estresse Fisiológico/genética , Fatores de Transcrição/genética , Vitamina D/farmacologia , Animais , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/fisiologia , Proteínas de Caenorhabditis elegans/metabolismo , Calcitriol/metabolismo , Proteínas de Transporte/metabolismo , Colecalciferol/metabolismo , Proteínas de Ligação a DNA/metabolismo , Retículo Endoplasmático/efeitos dos fármacos , Retículo Endoplasmático/metabolismo , Agregados Proteicos , Proteínas Serina-Treonina Quinases/metabolismo , Solubilidade , Fatores de Transcrição/metabolismo , Resposta a Proteínas não Dobradas/efeitos dos fármacosRESUMO
Metazoan introns contain a polypyrimidine tract immediately upstream of the AG dinucleotide that defines the 3' splice site. In the nematode Caenorhabditis elegans, 3' splice sites are characterized by a highly conserved UUUUCAG/R octamer motif. While the conservation of pyrimidines in this motif is strongly suggestive of their importance in pre-mRNA splicing, in vivo evidence in support of this is lacking. In an N-ethyl-N-nitrosourea (ENU) mutagenesis screen in Caenorhabditis elegans, we have isolated a strain containing a point mutation in the octamer motif of a 3' splice site in the daf-12 gene. This mutation, a single base T-to-G transversion at the -5 position relative to the splice site, causes a strong daf-12 loss-of-function phenotype by abrogating splicing. The resulting transcript is predicted to encode a truncated DAF-12 protein generated by translation into the retained intron, which contains an in-frame stop codon. Other than the perfectly conserved AG dinucleotide at the site of splicing, G at the -5 position of the octamer motif is the most uncommon base in C. elegans 3' splice sites, occurring at closely paired sites where the better match to the splicing consensus is a few bases downstream. Our results highlight both the biological importance of the highly conserved -5 uridine residue in the C. elegans 3' splice site octamer motif as well as the utility of using ENU as a mutagen to study the function of polypyrimidine tracts and other AU- or AT-rich motifs in vivo.
Assuntos
Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/genética , Etilnitrosoureia/toxicidade , Íntrons , Mutagênese/efeitos dos fármacos , Sítios de Splice de RNA , Animais , Sequência de Bases , Caenorhabditis elegans/metabolismo , Mapeamento Cromossômico , Mutação , Motivos de Nucleotídeos , Fenótipo , Polimorfismo de Nucleotídeo Único , Ligação Proteica , Fatores de Processamento de RNA/metabolismo , Deleção de SequênciaRESUMO
Chromoanasynthesis is a recently discovered phenomenon in humans with congenital diseases that is characterized by complex genomic rearrangements (CGRs) resulting from aberrant repair of catastrophic chromosomal damage. How these CGRs are induced is not known. Here, we describe the structure and function of dpDp667, a causative CGR that emerged from a Caenorhabditis elegans dauer suppressor screen in which animals were treated with the point mutagen N-ethyl-N-nitrosourea (ENU). dpDp667 comprises nearly 3 Mb of sequence on the right arm of the X chromosome, contains three duplications and one triplication, and is devoid of deletions. Sequences from three out of the four breakpoint junctions in dpDp667 reveal microhomologies that are hallmarks of chromoanasynthetic CGRs. Our findings suggest that environmental insults and physiological processes that cause point mutations may give rise to chromoanasynthetic rearrangements associated with congenital disease. The relatively subtle phenotype of animals harboring dpDp667 suggests that the prevalence of CGRs in the genomes of mutant and/or phenotypically unremarkable animals may be grossly underestimated.
Assuntos
Caenorhabditis elegans/genética , Rearranjo Gênico , Genoma Helmíntico , Genômica , Mutagênese , Animais , Caenorhabditis elegans/efeitos dos fármacos , Pontos de Quebra do Cromossomo , Etilnitrosoureia/toxicidade , Dosagem de Genes , Genômica/métodos , Mutagênese/efeitos dos fármacos , Análise de Sequência de DNA , Cromossomo XRESUMO
Small-molecule ligands of nuclear hormone receptors (NHRs) govern the transcriptional regulation of metazoan development, cell differentiation, and metabolism. However, the physiological ligands of many NHRs remain poorly characterized, primarily due to lack of robust analytical techniques. Using comparative metabolomics, we identified endogenous steroids that act as ligands of the C. elegans NHR, DAF-12, a vitamin D and liver X receptor homolog regulating larval development, fat metabolism, and lifespan. The identified molecules feature unexpected chemical modifications and include only one of two DAF-12 ligands reported earlier, necessitating a revision of previously proposed ligand biosynthetic pathways. We further show that ligand profiles are regulated by a complex enzymatic network, including the Rieske oxygenase DAF-36, the short-chain dehydrogenase DHS-16, and the hydroxysteroid dehydrogenase HSD-1. Our results demonstrate the advantages of comparative metabolomics over traditional candidate-based approaches and provide a blueprint for the identification of ligands for other C. elegans and mammalian NHRs.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/crescimento & desenvolvimento , Caenorhabditis elegans/metabolismo , Longevidade/fisiologia , Metabolômica , Receptores Citoplasmáticos e Nucleares/metabolismo , Animais , Colestenos/química , Colestenos/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Ligantes , Espectroscopia de Ressonância Magnética , Mutação/genética , Especificidade de Órgãos , Transdução de Sinais , Esteroides/metabolismoRESUMO
During embryogenesis, an essential process known as dosage compensation is initiated to equalize gene expression from sex chromosomes. Although much is known about how dosage compensation is established, the consequences of modulating the stability of dosage compensation postembryonically are not known. Here we define a role for the Caenorhabditis elegans dosage compensation complex (DCC) in the regulation of DAF-2 insulin-like signaling. In a screen for dauer regulatory genes that control the activity of the FoxO transcription factor DAF-16, we isolated three mutant alleles of dpy-21, which encodes a conserved DCC component. Knockdown of multiple DCC components in hermaphrodite and male animals indicates that the dauer suppression phenotype of dpy-21 mutants is due to a defect in dosage compensation per se. In dpy-21 mutants, expression of several X-linked genes that promote dauer bypass is elevated, including four genes encoding components of the DAF-2 insulin-like pathway that antagonize DAF-16/FoxO activity. Accordingly, dpy-21 mutation reduced the expression of DAF-16/FoxO target genes by promoting the exclusion of DAF-16/FoxO from nuclei. Thus, dosage compensation enhances dauer arrest by repressing X-linked genes that promote reproductive development through the inhibition of DAF-16/FoxO nuclear translocation. This work is the first to establish a specific postembryonic function for dosage compensation in any organism. The influence of dosage compensation on dauer arrest, a larval developmental fate governed by the integration of multiple environmental inputs and signaling outputs, suggests that the dosage compensation machinery may respond to external cues by modulating signaling pathways through chromosome-wide regulation of gene expression.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/crescimento & desenvolvimento , Mecanismo Genético de Compensação de Dose , Desenvolvimento Embrionário , Insulina/metabolismo , Fatores de Transcrição/genética , Animais , Caenorhabditis elegans/genética , Fatores de Transcrição Forkhead , Regulação da Expressão Gênica no Desenvolvimento , Genes Ligados ao Cromossomo X , Insulina/genética , Masculino , Mutação , Receptor de Insulina/genética , Transdução de SinaisRESUMO
The AGC family serine-threonine kinases Akt and Sgk are similar in primary amino acid sequence and in vitro substrate specificity, and both kinases are thought to directly phosphorylate and inhibit FoxO transcription factors. In the nematode Caenorhabditis elegans, it is well established that AKT-1 controls dauer arrest and lifespan by regulating the subcellular localization of the FoxO transcription factor DAF-16. SGK-1 is thought to act similarly to AKT-1 in lifespan control by phosphorylating and inhibiting the nuclear translocation of DAF-16/FoxO. Using sgk-1 null and gain-of-function mutants, we now provide multiple lines of evidence indicating that AKT-1 and SGK-1 influence C. elegans lifespan, stress resistance, and DAF-16/FoxO activity in fundamentally different ways. Whereas AKT-1 shortens lifespan, SGK-1 promotes longevity in a DAF-16-/FoxO-dependent manner. In contrast to AKT-1, which reduces resistance to multiple stresses, SGK-1 promotes resistance to oxidative stress and ultraviolet radiation but inhibits thermotolerance. Analysis of several DAF-16/FoxO target genes that are repressed by AKT-1 reveals that SGK-1 represses a subset of these genes while having little influence on the expression of others. Accordingly, unlike AKT-1, which promotes the cytoplasmic sequestration of DAF-16/FoxO, SGK-1 does not influence DAF-16/FoxO subcellular localization. Thus, in spite of their similar in vitro substrate specificities, Akt and Sgk influence longevity, stress resistance, and FoxO activity through distinct mechanisms in vivo. Our findings highlight the need for a re-evaluation of current paradigms of FoxO regulation by Sgk.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/genética , Longevidade/genética , Mutação , Proteínas Serina-Treonina Quinases/genética , Fatores de Transcrição/genética , Animais , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Feminino , Fatores de Transcrição Forkhead , Regulação da Expressão Gênica no Desenvolvimento , Masculino , Fosforilação , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais , Fatores de Transcrição/metabolismoRESUMO
Sterol-sensing nuclear receptors and insulin-like growth factor signaling play evolutionarily conserved roles in the control of aging. In the nematode Caenorhabditis elegans, bile acid-like steroid hormones known as dafachronic acids (DAs) influence longevity by binding to and regulating the activity of the conserved nuclear receptor DAF-12, and the insulin receptor (InsR) ortholog DAF-2 controls life span by inhibiting the FoxO transcription factor DAF-16. How the DA/DAF-12 pathway interacts with DAF-2/InsR signaling to control life span is poorly understood. Here we specifically investigated the roles of liganded and unliganded DAF-12 in life span control in the context of reduced DAF-2/InsR signaling. In animals with reduced daf-2/InsR activity, mutations that either reduce DA biosynthesis or fully abrogate DAF-12 activity shorten life span, suggesting that liganded DAF-12 promotes longevity. In animals with reduced DAF-2/InsR activity induced by daf-2/InsR RNAi, both liganded and unliganded DAF-12 promote longevity. However, in daf-2/InsR mutants, liganded and unliganded DAF-12 act in opposition to control life span. Thus, multiple DAF-12 activities influence life span in distinct ways in contexts of reduced DAF-2/InsR signaling. Our findings establish new roles for a conserved steroid signaling pathway in life span control and elucidate interactions among DA biosynthetic pathways, DAF-12, and DAF-2/InsR signaling in aging.
Assuntos
Caenorhabditis elegans/fisiologia , Hormônios/farmacologia , Insulina/metabolismo , Longevidade/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Esteroides/farmacologia , Animais , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Colestenos/metabolismo , Genes de Helmintos , Células Germinativas/efeitos dos fármacos , Células Germinativas/metabolismo , Ligantes , Modelos Biológicos , Mutação/genética , Receptor de Insulina/metabolismo , Transcrição Gênica/efeitos dos fármacosRESUMO
Recent work has identified changes in the metabolism of the aromatic amino acid tyrosine as a risk factor for diabetes and a contributor to the development of liver cancer. While these findings could suggest a role for tyrosine as a direct regulator of the behavior of cells and tissues, evidence for this model is currently lacking. Through the use of RNAi and genetic mutants, we identify tatn-1, which is the worm ortholog of tyrosine aminotransferase and catalyzes the first step of the conserved tyrosine degradation pathway, as a novel regulator of the dauer decision and modulator of the daf-2 insulin/IGF-1-like (IGFR) signaling pathway in Caenorhabditis elegans. Mutations affecting tatn-1 elevate tyrosine levels in the animal, and enhance the effects of mutations in genes that lie within the daf-2/insulin signaling pathway or are otherwise upstream of daf-16/FOXO on both dauer formation and worm longevity. These effects are mediated by elevated tyrosine levels as supplemental dietary tyrosine mimics the phenotypes produced by a tatn-1 mutation, and the effects still occur when the enzymes needed to convert tyrosine into catecholamine neurotransmitters are missing. The effects on dauer formation and lifespan require the aak-2/AMPK gene, and tatn-1 mutations increase phospho-AAK-2 levels. In contrast, the daf-16/FOXO transcription factor is only partially required for the effects on dauer formation and not required for increased longevity. We also find that the controlled metabolism of tyrosine by tatn-1 may function normally in dauer formation because the expression of the TATN-1 protein is regulated both by daf-2/IGFR signaling and also by the same dietary and environmental cues which influence dauer formation. Our findings point to a novel role for tyrosine as a developmental regulator and modulator of longevity, and support a model where elevated tyrosine levels play a causal role in the development of diabetes and cancer in people.
Assuntos
Proteínas de Caenorhabditis elegans/genética , Caenorhabditis elegans/crescimento & desenvolvimento , Longevidade/genética , Redes e Vias Metabólicas/genética , Tirosina Transaminase/genética , Tirosina/genética , Animais , Animais Geneticamente Modificados , Caenorhabditis elegans/genética , Fatores de Transcrição Forkhead , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Fluorescência Verde , Humanos , Insulina/metabolismo , Fator de Crescimento Insulin-Like I/metabolismo , Larva/genética , Larva/crescimento & desenvolvimento , Larva/metabolismo , Mutação , Interferência de RNA , Receptor de Insulina/metabolismo , Fatores de Transcrição/genética , Tirosina/metabolismoRESUMO
FoxO transcription factors (TFs) extend lifespan in invertebrates and may participate in the control of human longevity. The role of FoxO TFs in lifespan regulation has been studied most extensively inC. elegans, where a conserved insulin/insulin-like growth factor signaling (IIS) pathway and the germline both control lifespan by regulating the subcellular localization of the FoxO transcription factor DAF-16. Although the control of FoxO activity through modulation of its subcellular localization is well established, nuclear translocation of FoxO is not sufficient for full FoxO activation, suggesting that undiscovered inputs regulate FoxO activity after its translocation to the nucleus. We have recently discovered a new conserved pathway, the EAK (enhancer-of-akt-1) pathway, which acts in parallel to the Akt/PKB family of serine-threonine kinases to regulate DAF-16/FoxO activity. Whereas mutation of Akt/PKB promotes the nuclear accumulation of DAF-16/FoxO, mutation of eak genes increases nuclear DAF-16/FoxO activity without influencing DAF-16/FoxO subcellular localization. Thus, EAK proteins regulate the activity of nuclear DAF-16/FoxO. Two EAK proteins, EAK-2/HSD-1 and EAK-7, influence C. elegans lifespan and are conserved in mammals. The discovery of the EAK pathway defines a new conserved FoxO regulatory input and may have implications relevant to aging and the pathogenesis of aging-associated diseases.
Assuntos
Proteínas de Caenorhabditis elegans/fisiologia , Caenorhabditis elegans/fisiologia , Longevidade/fisiologia , 3-Hidroxiesteroide Desidrogenases/genética , 3-Hidroxiesteroide Desidrogenases/metabolismo , Transporte Ativo do Núcleo Celular/fisiologia , Envelhecimento/fisiologia , Animais , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Diabetes Mellitus Tipo 2/etiologia , Diabetes Mellitus Tipo 2/metabolismo , Doença/etiologia , Fatores de Transcrição Forkhead/metabolismo , Humanos , Camundongos , Modelos Biológicos , Osteoporose/etiologia , Osteoporose/metabolismo , Oxigenases/metabolismo , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais/fisiologia , Fatores de Transcrição/metabolismoRESUMO
FoxO transcription factors control development and longevity in diverse species. Although FoxO regulation via changes in its subcellular localization is well established, little is known about how FoxO activity is regulated in the nucleus. Here, we show that the conserved C. elegans protein EAK-7 acts in parallel to the serine/threonine kinase AKT-1 to inhibit the FoxO transcription factor DAF-16. Loss of EAK-7 activity promotes diapause and longevity in a DAF-16/FoxO-dependent manner. Whereas akt-1 mutation activates DAF-16/FoxO by promoting its translocation from the cytoplasm to the nucleus, eak-7 mutation increases nuclear DAF-16/FoxO activity without influencing DAF-16/FoxO subcellular localization. Thus, EAK-7 and AKT-1 inhibit DAF-16/FoxO activity via distinct mechanisms. Our results implicate EAK-7 as a FoxO regulator and highlight the biological impact of a regulatory pathway that governs the activity of nuclear FoxO without altering its subcellular location.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Transporte/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Fatores de Transcrição/metabolismo , Animais , Caenorhabditis elegans , Proteínas de Caenorhabditis elegans/genética , Proteínas de Transporte/genética , Longevidade , Mutação , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Interferência de RNARESUMO
Steroid hormone and insulin/insulin-like growth factor signaling (IIS) pathways control development and lifespan in the nematode Caenorhabditis elegans by regulating the activity of the nuclear receptor DAF-12 and the FoxO transcription factor DAF-16, respectively. The DAF-12 ligands Delta(4)- and Delta(7)-dafachronic acid (DA) promote bypass of the dauer diapause and proper gonadal migration during larval development; in adults, DAs influence lifespan. Whether Delta(4)- and Delta(7)-DA have unique biological functions is not known. We identified the 3-beta-hydroxysteroid dehydrogenase (3betaHSD) family member HSD-1, which participates in Delta(4)-DA biosynthesis, as an inhibitor of DAF-16/FoxO activity. Whereas IIS promotes the cytoplasmic sequestration of DAF-16/FoxO, HSD-1 inhibits nuclear DAF-16/FoxO activity without affecting DAF-16/FoxO subcellular localization. Thus, HSD-1 and IIS inhibit DAF-16/FoxO activity via distinct and complementary mechanisms. In adults, HSD-1 was required for full lifespan extension in IIS mutants, indicating that HSD-1 interactions with IIS are context-dependent. In contrast to the Delta(7)-DA biosynthetic enzyme DAF-36, HSD-1 is dispensable for proper gonadal migration and lifespan extension induced by germline ablation. These findings provide insights into the molecular interface between DA and IIS pathways and suggest that Delta(4)- and Delta(7)-DA pathways have unique as well as overlapping biological functions in the control of development and lifespan.