ABSTRACT
The C. elegans insulin/IGF-1 signaling (IIS) cascade plays a central role in regulating life span, dauer, metabolism, and stress. The major regulatory control of IIS is through phosphorylation of its components by serine/threonine-specific protein kinases. An RNAi screen for serine/threonine protein phosphatases that counterbalance the effect of the kinases in the IIS pathway identified pptr-1, a B56 regulatory subunit of the PP2A holoenzyme. Modulation of pptr-1 affects IIS pathway-associated phenotypes including life span, dauer, stress resistance, and fat storage. We show that PPTR-1 functions by regulating worm AKT-1 phosphorylation at Thr 350. With striking conservation, mammalian B56beta regulates Akt phosphorylation at Thr 308 in 3T3-L1 adipocytes. In C. elegans, this ultimately leads to changes in subcellular localization and transcriptional activity of the forkhead transcription factor DAF-16. This study reveals a conserved role for the B56 regulatory subunit in regulating insulin signaling through AKT dephosphorylation, thereby having widespread implications in cancer and diabetes research.
Subject(s)
Caenorhabditis elegans Proteins/metabolism , Caenorhabditis elegans/metabolism , Insulin-Like Growth Factor I/metabolism , Insulin/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction , Animals , Caenorhabditis elegans/growth & development , Longevity , Phosphoric Monoester Hydrolases/analysis , Phosphorylation , Receptors, Cell Surface/metabolismABSTRACT
Homologous recombination (HR) is an important conserved process for DNA repair and ensures maintenance of genome integrity. Inappropriate HR causes gross chromosomal rearrangements and tumorigenesis in mammals. In yeast, the Srs2 helicase eliminates inappropriate recombination events, but the functional equivalent of Srs2 in higher eukaryotes has been elusive. Here, we identify C. elegans RTEL-1 as a functional analog of Srs2 and describe its vertebrate counterpart, RTEL1, which is required for genome stability and tumor avoidance. We find that rtel-1 mutant worms and RTEL1-depleted human cells share characteristic phenotypes with yeast srs2 mutants: lethality upon deletion of the sgs1/BLM homolog, hyperrecombination, and DNA damage sensitivity. In vitro, purified human RTEL1 antagonizes HR by promoting the disassembly of D loop recombination intermediates in a reaction dependent upon ATP hydrolysis. We propose that loss of HR control after deregulation of RTEL1 may be a critical event that drives genome instability and cancer.
Subject(s)
Caenorhabditis elegans Proteins/metabolism , Caenorhabditis elegans/enzymology , DNA Helicases/metabolism , Genomic Instability , Recombination, Genetic , Animals , Caenorhabditis elegans/genetics , Caenorhabditis elegans/metabolism , Caenorhabditis elegans Proteins/genetics , DNA/metabolism , DNA Helicases/genetics , DNA Repair , Humans , Mutation , Saccharomyces cerevisiae/enzymology , Saccharomyces cerevisiae Proteins/metabolismABSTRACT
As Western diets continue to include an ever-increasing amount of sugar, there has been a rise in obesity and type 2 diabetes. To avoid metabolic diseases, the body must maintain proper metabolism, even on a high-sugar diet. In both humans and Caenorhabditis elegans, excess sugar (glucose) is stored as glycogen. Here, we find that animals increased stored glycogen as they aged, whereas even young adult animals had increased stored glycogen on a high-sugar diet. Decreasing the amount of glycogen storage by modulating the C. elegans glycogen synthase, gsy-1, a key enzyme in glycogen synthesis, can extend lifespan, prolong healthspan, and limit the detrimental effects of a high-sugar diet. Importantly, limiting glycogen storage leads to a metabolic shift whereby glucose is now stored as trehalose. Two additional means to increase trehalose show similar longevity extension. Increased trehalose is entirely dependent on a functional FOXO transcription factor DAF-16 and autophagy to promote lifespan and healthspan extension. Our results reveal that when glucose is stored as glycogen, it is detrimental, whereas, when stored as trehalose, animals live a longer, healthier life if DAF-16 is functional. Taken together, these results demonstrate that trehalose modulation may be an avenue for combatting high-sugar-diet pathology.
Subject(s)
Caenorhabditis elegans/metabolism , Glycogen/metabolism , Trehalose/metabolism , Animals , Animals, Genetically Modified , Autophagy/physiology , Caenorhabditis elegans/drug effects , Caenorhabditis elegans/genetics , Caenorhabditis elegans Proteins/genetics , Caenorhabditis elegans Proteins/metabolism , Forkhead Transcription Factors/genetics , Forkhead Transcription Factors/metabolism , Glucose/metabolism , Glucose/toxicity , Glycogen/genetics , Longevity , Time Factors , Trehalose/geneticsABSTRACT
Aging research has been very successful at identifying signaling pathways and evolutionarily conserved genes that extend lifespan with the assumption that an increase in lifespan will also increase healthspan. However, it is largely unknown whether we are extending the healthy time of life or simply prolonging a period of frailty with increased incidence of age-associated diseases. Here we use Caenorhabditis elegans, one of the premiere systems for lifespan studies, to determine whether lifespan and healthspan are intrinsically correlated. We conducted multiple cellular and organismal assays on wild type as well as four long-lived mutants (insulin/insulin-like growth factor-1, dietary restriction, protein translation, mitochondrial signaling) in a longitudinal manner to determine the health of the animals as they age. We find that some long-lived mutants performed better than wild type when measured chronologically (number of days). However, all long-lived mutants increased the proportion of time spent in a frail state. Together, these data suggest that lifespan can no longer be the sole parameter of interest and reveal the importance of evaluating multiple healthspan parameters for future studies on antiaging interventions.
Subject(s)
Caenorhabditis elegans/physiology , Longevity/genetics , Mutation , Animals , Caenorhabditis elegans/genetics , MovementABSTRACT
Gene families expand by gene duplication, and resulting paralogs diverge through mutation. Functional diversification can include neofunctionalization as well as subfunctionalization of ancestral functions. In addition, redundancy in which multiple genes fulfill overlapping functions is often maintained. Here, we use the family of 40 Caenorhabditis elegans insulins to gain insight into the balance between specificity and redundancy. The insulin/insulin-like growth factor (IIS) pathway comprises a single receptor, DAF-2. To date, no single insulin-like peptide recapitulates all DAF-2-associated phenotypes, likely due to redundancy between insulin-like genes. To provide a first-level annotation of potential patterns of redundancy, we comprehensively delineate the spatiotemporal and conditional expression of all 40 insulins in living animals. We observe extensive dynamics in expression that can explain the lack of simple patterns of pairwise redundancy. We propose a model in which gene families evolve to attain differential alliances in different tissues and in response to a range of environmental stresses.
Subject(s)
Caenorhabditis elegans/genetics , Caenorhabditis elegans/metabolism , Gene Expression Regulation , Insulin/genetics , Insulin/metabolism , Signal Transduction , Animals , Cluster Analysis , Gene Expression Profiling , Gene Expression Regulation, Developmental , Gene Regulatory Networks , RNA InterferenceABSTRACT
The insulin/IGF-1 signalling (IIS) pathway has diverse roles from metabolism to longevity. In Caenorhabditis elegans, the single forkhead box O (FOXO) homologue, DAF-16, functions as the major target of the IIS pathway. One of two isoforms, DAF-16a, is known to regulate longevity, stress response and dauer diapause. However, it remains unclear how DAF-16 achieves its specificity in regulating these various biological processes. Here we identify a new isoform, DAF-16d/f, as an important isoform regulating longevity. We show that DAF-16 isoforms functionally cooperate to modulate IIS-mediated processes through differential tissue enrichment, preferential modulation by upstream kinases, and regulating distinct and overlapping target genes. Promoter-swapping experiments show both the promoter and the coding region of DAF-16 are important for its function. Importantly, in mammals, four FOXO genes have overlapping and different functions, and in C. elegans, a single FOXO/DAF-16 uses distinct isoforms to fine-tune the IIS-mediated processes in the context of a whole organism.
Subject(s)
Caenorhabditis elegans Proteins/metabolism , Caenorhabditis elegans/physiology , Longevity/physiology , Transcription Factors/metabolism , Active Transport, Cell Nucleus , Animals , Animals, Genetically Modified , Caenorhabditis elegans/enzymology , Caenorhabditis elegans/genetics , Caenorhabditis elegans/metabolism , Caenorhabditis elegans Proteins/chemistry , Caenorhabditis elegans Proteins/genetics , Forkhead Transcription Factors , Gene Expression Regulation , Insulin/metabolism , Insulin-Like Growth Factor I/metabolism , Longevity/genetics , Mutation , Organ Specificity , Phosphatidylinositol 3-Kinases/metabolism , Promoter Regions, Genetic , Protein Isoforms/chemistry , Protein Isoforms/genetics , Protein Isoforms/metabolism , Proto-Oncogene Proteins c-akt/genetics , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction , Superoxide Dismutase/genetics , Transcription Factors/chemistry , Transcription Factors/genetics , TransgenesABSTRACT
DAF-16, a forkhead transcription factor, is a key regulator of longevity, metabolism and dauer diapause in Caenorhabditis elegans. The precise mechanism by which DAF-16 regulates multiple functions, however, is poorly understood. Here, we used chromatin immunoprecipitation (ChIP) to identify direct targets of DAF-16. We cloned 103 target sequences containing consensus DAF-16 binding sites and selected 33 targets for further analysis. Expression of most of these genes is regulated in a DAF-16-dependent manner, and inactivation of more than half of these genes significantly altered DAF-16-dependent functions, including life span, fat storage and dauer formation. Our results show that the ChIP-based cloning strategy leads to greater enrichment for DAF-16 target genes than previous screening strategies. We also demonstrate that DAF-16 is recruited to multiple promoters to coordinate regulation of its downstream targets. The large number of target genes discovered provides insight into how DAF-16 controls diverse biological functions.
Subject(s)
Caenorhabditis elegans Proteins/metabolism , Caenorhabditis elegans/metabolism , Longevity/physiology , Transcription Factors/metabolism , Alleles , Animals , Caenorhabditis elegans/physiology , Chromatin Immunoprecipitation , Forkhead Transcription Factors , Gene Expression Regulation , Genes, Helminth , PhenotypeABSTRACT
Over a century ago, the zoologist Emile Maupas first identified the nematode, Rhabditis elegans, in the soil in Algiers. Subsequent work and phylogenic studies renamed the species Caenorhabditis elegans or more commonly referred to as C. elegans; (Caeno meaning recent; rhabditis meaning rod; elegans meaning nice). However, it was not until 1963, when Sydney Brenner, already successful from his work on DNA, RNA, and the genetic code, suggested the future of biological research lay in model organisms. Brenner believed that biological research required a model system that could grow in vast quantities in the lab, were cheap to maintain and had a simple body plan, and he chose the nematode C. elegans to fulfill such a role. Since that time, C. elegans has emerged as one of the premiere model systems for aging research. This paper reviews some initial identification of mutants with altered lifespan with a focus on genetics and then discusses advantages and disadvantages for using C. elegans as a model system to understand human aging. This review focuses on molecular genetics aspects of this model organism.
ABSTRACT
The insulin/IGF-1 signaling (IIS) pathway is a conserved regulator of longevity, development, and metabolism. In Caenorhabditis elegans IIS involves activation of DAF-2 (insulin/IGF-1 receptor tyrosine kinase), AGE-1 (PI 3-kinase), and additional downstream serine/threonine kinases that ultimately phosphorylate and negatively regulate the single FOXO transcription factor homolog DAF-16. Phosphatases help to maintain cellular signaling homeostasis by counterbalancing kinase activity. However, few phosphatases have been identified that negatively regulate the IIS pathway. Here we identify and characterize pdp-1 as a novel negative modulator of the IIS pathway. We show that PDP-1 regulates multiple outputs of IIS such as longevity, fat storage, and dauer diapause. In addition, PDP-1 promotes DAF-16 nuclear localization and transcriptional activity. Interestingly, genetic epistasis analyses place PDP-1 in the DAF-7/TGF-ß signaling pathway, at the level of the R-SMAD proteins DAF-14 and DAF-8. Further investigation into how a component of TGF-ß signaling affects multiple outputs of IIS/DAF-16, revealed extensive crosstalk between these two well-conserved signaling pathways. We find that PDP-1 modulates the expression of several insulin genes that are likely to feed into the IIS pathway to regulate DAF-16 activity. Importantly, dysregulation of IIS and TGF-ß signaling has been implicated in diseases such as Type 2 Diabetes, obesity, and cancer. Our results may provide a new perspective in understanding of the regulation of these pathways under normal conditions and in the context of disease.
Subject(s)
Caenorhabditis elegans Proteins/metabolism , Caenorhabditis elegans/enzymology , Longevity/genetics , Pyruvate Dehydrogenase (Lipoamide)-Phosphatase/metabolism , Receptor, Insulin/metabolism , Transcription Factors/metabolism , Animals , Animals, Genetically Modified/genetics , Animals, Genetically Modified/growth & development , Animals, Genetically Modified/metabolism , Caenorhabditis elegans/genetics , Caenorhabditis elegans/growth & development , Forkhead Transcription Factors , Gene Expression Regulation, Developmental , Insulin/metabolism , Mutation , Phenotype , Pyruvate Dehydrogenase (Lipoamide)-Phosphatase/genetics , RNA Interference , Receptor, IGF Type 1/genetics , Receptor, IGF Type 1/metabolism , Receptors, Transforming Growth Factor beta/metabolism , Signal TransductionABSTRACT
Quantitation of lipid storage, unsaturation, and oxidation in live C.â elegans has been a long-standing obstacle. The combination of hyperspectral stimulated Raman scattering imaging and multivariate analysis in the fingerprint vibration region represents a platform that allows the quantitative mapping of fat distribution, degree of fat unsaturation, lipid oxidation, and cholesterol storage inâ vivo in the whole worm. Our results reveal for the first time that lysosome-related organelles in intestinal cells are sites for storage of cholesterol in C.â elegans.
Subject(s)
Caenorhabditis elegans/chemistry , Lipids/chemistry , Metabolic Networks and Pathways , Spectrum Analysis/methods , Animals , Dermatoglyphics , VibrationABSTRACT
Aging is linked to a time-associated decline in both cellular function and repair capacity leading to malfunction on an organismal level, increased frailty, higher incidence of diseases, and death. As the population grows older, there is a need to reveal mechanisms associated with aging that could spearhead treatments to postpone the onset of age-associated decline, extend both healthspan and lifespan. One possibility is targeting the sirtuin SIRT1, the founding member of the sirtuin family, a highly conserved family of histone deacetylases that have been linked to metabolism, stress response, protein synthesis, genomic instability, neurodegeneration, DNA damage repair, and inflammation. Importantly, sirtuins have also been implicated to promote health and lifespan extension, while their dysregulation has been linked to cancer, neurological processes, and heart disorders. SIRT1 is one of seven members of sirtuin family; each requiring nicotinamide adenine dinucleotide (NAD+) as co-substrate for their catalytic activity. Overexpression of yeast, worm, fly, and mice SIRT1 homologs extend lifespan in each animal, respectively. Moreover, lifespan extension due to calorie restriction are associated with increased sirtuin activity. These findings led to the search for a calorie restriction mimetic, which revealed the compound resveratrol; (3, 5, 4'-trihydroxy-trans-stilbene) belonging to the stilbenoids group of polyphenols. Following this finding, resveratrol and other sirtuin-activating compounds have been extensively studied for their ability to affect health and lifespan in a variety of species, including humans via clinical studies.
ABSTRACT
Overconsumption of dietary sugar can lead to many negative health effects including the development of Type 2 diabetes, metabolic syndrome, cardiovascular disease, and neurodegenerative disorders. Recently, the human intestinal microbiota, strongly associated with our overall health, has also been known to be affected by diet. However, mechanistic insight into the importance of the human intestinal microbiota and the effects of chronic sugar ingestion has not been possible largely due to the complexity of the human microbiome which contains hundreds of types of organisms. Here, we use an interspecies C. elegans/E. coli system, where E. coli are subjected to high sugar, then consumed by the bacterivore host C. elegans to become the microbiota. This glucose-fed microbiota results in a significant lifespan reduction accompanied by reduced healthspan (locomotion), reduced stress resistance, and changes in behavior and feeding. Lifespan reduction is also accompanied by two potential major contributors: increased intestinal bacterial density and increased concentration of reactive oxygen species. The glucose-fed microbiota accelerated the age-related development of intestinal cell permeability, intestinal distention, and dysregulation of immune effectors. Ultimately, the changes in the intestinal epithelium due to aging with the glucose-fed microbiota results in increased susceptibility to multiple bacterial pathogens. Taken together, our data reveal that chronic ingestion of sugar, such as a Western diet, has profound health effects on the host due to changes in the microbiota and may contribute to the current increased incidence of ailments including inflammatory bowel diseases as well as multiple age-related diseases.
Subject(s)
Caenorhabditis elegans , Escherichia coli , Gastrointestinal Microbiome , Glucose , Intestinal Mucosa , Caenorhabditis elegans/microbiology , Animals , Glucose/metabolism , Intestinal Mucosa/microbiology , Intestinal Mucosa/metabolism , Reactive Oxygen Species/metabolism , Longevity , Disease SusceptibilityABSTRACT
One of the current challenges of neurodegenerative disease research is to determine whether signaling pathways that are essential to cellular homeostasis might contribute to neuronal survival and modulate the pathogenic process in human disease. In Caenorhabditis elegans, sir-2.1/SIRT1 overexpression protects neurons from the early phases of expanded polyglutamine (polyQ) toxicity, and this protection requires the longevity-promoting factor daf-16/FOXO. Here, we show that this neuroprotective effect also requires the DAF-16/FOXO partner bar-1/ß-catenin and putative DAF-16-regulated gene ucp-4, the sole mitochondrial uncoupling protein (UCP) in nematodes. These results fit with a previously proposed mechanism in which the ß-catenin FOXO and SIRT1 proteins may together regulate gene expression and cell survival. Knockdown of ß-catenin enhanced the vulnerability to cell death of mutant-huntingtin striatal cells derived from the HdhQ111 knock-in mice. In addition, this effect was compensated by SIRT1 overexpression and accompanied by the modulation of neuronal UCP expression levels, further highlighting a cross-talk between ß-catenin and SIRT1 in the modulation of mutant polyQ cytoxicity. Taken together, these results suggest that integration of ß-catenin, sirtuin and FOXO signaling protects from the early phases of mutant huntingtin toxicity.
Subject(s)
Caenorhabditis elegans Proteins/biosynthesis , Caenorhabditis elegans Proteins/physiology , Cytoskeletal Proteins/biosynthesis , Nerve Tissue Proteins/toxicity , Signal Transduction/physiology , Sirtuins/physiology , Transcription Factors/biosynthesis , beta Catenin/biosynthesis , Animals , Animals, Genetically Modified , Caenorhabditis elegans , Caenorhabditis elegans Proteins/genetics , Cell Survival/drug effects , Cell Survival/physiology , Cytoskeletal Proteins/genetics , Forkhead Transcription Factors , Huntingtin Protein , Nerve Tissue Proteins/antagonists & inhibitors , Nerve Tissue Proteins/genetics , Sirtuins/genetics , Transcription Factors/genetics , beta Catenin/geneticsABSTRACT
Neurotransmitters relay signals within the brain and to peripheral tissues, allowing communication between nerve cells. New work from in this issue of Cell Metabolism reveals that, in C. elegans, serotonin functions during conditions of stress through the well-characterized insulin/IGF-1 signaling pathway, suggesting a mechanism for the stress response.
Subject(s)
Caenorhabditis elegans Proteins/metabolism , Caenorhabditis elegans/metabolism , Neurons/metabolism , Serotonin/metabolism , Signal Transduction , Transcription Factors/metabolism , Active Transport, Cell Nucleus/genetics , Animals , Animals, Genetically Modified , Caenorhabditis elegans/genetics , Caenorhabditis elegans Proteins/genetics , Cell Nucleus/genetics , Cell Nucleus/metabolism , Fluoxetine/pharmacology , Forkhead Transcription Factors/genetics , Forkhead Transcription Factors/metabolism , Models, Animal , Mutation , Neurosecretory Systems/metabolism , Receptor, IGF Type 1/genetics , Receptor, IGF Type 1/immunology , Receptor, Insulin/genetics , Receptor, Insulin/metabolism , Serotonin/genetics , Selective Serotonin Reuptake Inhibitors/pharmacology , Signal Transduction/drug effects , Transcription Factors/geneticsABSTRACT
Intestinal microbiota play an essential role in the health of a host organism. Here, we define how commensal Escherichia coli (E. coli) alters its host after long term exposure to glucose using a Caenorhabditis elegans-E. coli system where only the bacteria have direct contact with glucose. Our data reveal that bacterial processing of glucose results in reduced lifespan and healthspan including reduced locomotion, oxidative stress resistance, and heat stress resistance in C. elegans. With chronic exposure to glucose, E. coli exhibits growth defects and increased advanced glycation end products. These negative effects are abrogated when the E. coli is not able to process the additional glucose and by the addition of the anti-glycation compound carnosine. Physiological changes of the host C. elegans are accompanied by dysregulation of detoxifying genes including glyoxalase, glutathione-S-transferase, and superoxide dismutase. Loss of the glutathione-S-transferase, gst-4 shortens C. elegans lifespan and blunts the animal's response to a glucose fed bacterial diet. Taken together, we reveal that added dietary sugar may alter intestinal microbial E. coli to decrease lifespan and healthspan of the host and define a critical role of detoxification genes in maintaining health during a chronic high-sugar diet.
Subject(s)
Bacterial Physiological Phenomena , Caenorhabditis elegans/physiology , Glucose/metabolism , Longevity , Symbiosis , Animals , Energy Metabolism , Escherichia coli/physiologyABSTRACT
In C. elegans, similar to in mammals, mutations in the tubby homolog, tub-1, promote increased fat deposition. Here, we show that mutation in tub-1 also leads to life span extension dependent on daf-16/FOXO. Interestingly, function of tub-1 in fat storage is independent of daf-16. A yeast two-hybrid screen identified a novel TUB-1 interaction partner (RBG-3); a RabGTPase-activating protein. Both TUB-1 and RBG-3 localize to overlapping neurons. Importantly, RNAi of rbg-3 decreases fat deposition in tub-1 mutants but does not affect life span. We demonstrate that TUB-1 is expressed in ciliated neurons and undergoes both dendritic and ciliary transport. Additionally, tub-1 mutants are chemotaxis defective. Thus, tub-1 may regulate fat storage either by modulating transport, sensing, or responding to signals in ciliated neurons. Taken together, we define a role for tub-1 in regulation of life span and show that tub-1 regulates life span and fat storage by two independent mechanisms.
Subject(s)
Adipose Tissue/metabolism , Caenorhabditis elegans Proteins/metabolism , Caenorhabditis elegans/physiology , Lipid Metabolism , Longevity/physiology , Amino Acid Sequence , Animals , Caenorhabditis elegans/genetics , Caenorhabditis elegans Proteins/chemistry , Caenorhabditis elegans Proteins/genetics , Chemotaxis , Cilia/physiology , Forkhead Transcription Factors , Insulin/metabolism , Insulin-Like Growth Factor I/metabolism , Longevity/genetics , Models, Biological , Molecular Sequence Data , Mutation/genetics , Neurons/cytology , Neurons/metabolism , Protein Binding , Protein Transport , RNA Interference , Sequence Alignment , Transcription Factors/metabolism , rab GTP-Binding Proteins/chemistry , rab GTP-Binding Proteins/metabolismABSTRACT
Recent studies on aging in model systems such as yeast and roundworms have revealed conserved regulation of the process in response to nutrient availability and specific genes that appear to mediate this regulation. Here we review these findings with a focus on the nematode Caenorhabditis elegans and the budding yeast Saccharomyces cerevisiae and highlight general features of the regulation of aging that may have implications for mammals.
Subject(s)
Aging/physiology , Caenorhabditis elegans/physiology , Saccharomyces cerevisiae/physiology , Animals , Mammals , Models, AnimalABSTRACT
In Caenorhabditis elegans, there is a single FOXO transcription factor homolog, encoded by the gene, daf-16. As a central regulator for multiple signaling pathways, DAF-16 integrates these signals which results in modulation of several biological processes including longevity, development, fat storage, stress resistance, innate immunity, and reproduction. Using C. elegans allows for studies of FOXO in the context of the whole animal. Therefore, manipulating levels or the activity of daf-16 results in phenotypic changes. Genetic and molecular analysis revealed that similar to other systems, DAF-16 is the downstream target of the conserved insulin/IGF-1 signaling (IIS) pathway; a PI 3-kinase/AKT signaling cascade that ultimately controls the regulation of DAF-16 nuclear localization. In this chapter, I will focus on understanding how a single gene daf-16 can incorporate signals from multiple upstream pathways and in turn modulate different phenotypes as well as the study of FOXO in the context of a whole organism.
Subject(s)
Caenorhabditis elegans Proteins/genetics , Caenorhabditis elegans/genetics , Forkhead Transcription Factors/genetics , Gene Expression Regulation, Developmental , Longevity/genetics , Animals , Caenorhabditis elegans/growth & development , Caenorhabditis elegans Proteins/metabolism , Cell Nucleus/genetics , Cell Nucleus/metabolism , Forkhead Transcription Factors/metabolism , Mutation , Phenotype , Signal Transduction/geneticsABSTRACT
The conserved SIR2 protein regulates life span in both yeast and worms: in both organisms overexpression of SIR2 can extend life span and in Caenorhabditis elegans this life span extension is dependent on the forkhead transcription factor, DAF-16. Here, we have done extensive genetic analysis with sir-2.1(ok434), a null mutant of C. elegans sir-2.1, the closest homolog to yeast Sir2p and human SIRT1 to further elucidate its function in life span regulation. sir-2.1(ok434) mutants show a slight decrease in life span as well as sensitivity to various stresses. Our genetic analysis suggests that sir-2.1 is required for life span extension by caloric restriction, independent of the insulin/IGF-1 signaling pathway. Importantly, analysis with unc-13 mutants indicates that sir-2.1 and daf-16 have overlapping and distinct roles in life span regulation. Our expression analysis shows that sir-2.1 has overlapping and distinct expression pattern compared with daf-16, consistent with the results from our genetic data. Our data defines a central role for C. elegans SIR2 in regulation of life span by caloric restriction and demonstrates that sir-2.1 and daf-16 have both overlapping and distinct functions in regulation of C. elegans life span.
Subject(s)
Caenorhabditis elegans Proteins/metabolism , Caenorhabditis elegans/metabolism , Sirtuins/metabolism , Transcription Factors/metabolism , Aging/physiology , Animals , Caenorhabditis elegans/genetics , Caenorhabditis elegans Proteins/genetics , Forkhead Transcription Factors , Gene Expression Regulation , Mutation/genetics , Sirtuins/genetics , Time Factors , Transcription Factors/geneticsABSTRACT
14-3-3 proteins are evolutionarily conserved and ubiquitous proteins that function in a wide variety of biological processes. Here we define a new role for C. elegans 14-3-3 proteins in life span regulation. We identify two C. elegans 14-3-3 proteins as interacting proteins of a major life span regulator, the C. elegans SIR2 ortholog, SIR-2.1. Similar to sir-2.1, we find that overexpression of either 14-3-3 protein (PAR-5 or FTT-2) extends life span and that this is dependent on DAF-16, a forkhead transcription factor (FOXO), another important life span regulator in the insulin/IGF-1 signaling pathway. Furthermore, we show that both 14-3-3 proteins are co-expressed with DAF-16 and SIR-2.1 in the tissues critical for life span regulation. Finally, we show that DAF-16/FOXO also physically interacts with the 14-3-3 proteins. These results suggest that C. elegans 14-3-3 proteins can regulate longevity by cooperating with both SIR-2.1 and DAF-16/FOXO.