FOXO Transcription Factor DAF-16 Research Articles

RPN-6 determines C. elegans longevity under proteotoxic stress conditions

Organisms that protect their germ-cell lineages from damage often do so at considerable cost: limited metabolic resources become partitioned away from maintenance of the soma, leaving the ageing somatic tissues to navigate survival amid an environment containing damaged and poorly functioning proteins. Historically, experimental paradigms that limit reproductive investment result in lifespan extension. We proposed that germline-deficient animals might exhibit heightened protection from proteotoxic stressors in somatic tissues. We find that the forced re-investment of resources from the germ line to the soma in Caenorhabditis elegans results in elevated somatic proteasome activity, clearance of damaged proteins and increased longevity. This activity is associated with increased expression of rpn-6, a subunit of the 19S proteasome, by the FOXO transcription factor DAF-16. Ectopic expression of rpn-6 is sufficient to confer proteotoxic stress resistance and extend lifespan, indicating that rpn-6 is a candidate to correct deficiencies in age-related protein homeostasis disorders.

APL-1, the Alzheimer’s Amyloid Precursor Protein inCaenorhabditis elegans, Modulates Multiple Metabolic Pathways Throughout Development

Mutations in the amyloid precursor protein (APP) gene or in genes that process APP are correlated with familial Alzheimer's disease (AD). The biological function of APP remains unclear. APP is a transmembrane protein that can be sequentially cleaved by different secretases to yield multiple fragments, which can potentially act as signaling molecules. Caenorhabditis elegans encodes one APP-related protein, APL-1, which is essential for viability. Here, we show that APL-1 signaling is dependent on the activity of the FOXO transcription factor DAF-16 and the nuclear hormone receptor DAF-12 and influences metabolic pathways such as developmental progression, body size, and egg-laying rate. Furthermore, apl-1(yn5) mutants, which produce high levels of the extracellular APL-1 fragment, show an incompletely penetrant temperature-sensitive embryonic lethality. In a genetic screen to isolate mutants in which the apl-1(yn5) lethality rate is modified, we identified a suppressor mutation in MOA-1/R155.2, a receptor-protein tyrosine phosphatase, and an enhancer mutation in MOA-2/B0495.6, a protein involved in receptor-mediated endocytosis. Knockdown of apl-1 in an apl-1(yn5) background caused lethality and molting defects at all larval stages, suggesting that apl-1 is required for each transitional molt. We suggest that signaling of the released APL-1 fragment modulates multiple metabolic states and that APL-1 is required throughout development.

C. elegans rrf-1 Mutations Maintain RNAi Efficiency in the Soma in Addition to the Germline

Gene inactivation through RNA interference (RNAi) has proven to be a valuable tool for studying gene function in C. elegans. When combined with tissue-specific gene inactivation methods, RNAi has the potential to shed light on the function of a gene in distinct tissues. In this study we characterized C. elegans rrf-1 mutants to determine their ability to process RNAi in various tissues. These mutants have been widely used in RNAi studies to assess the function of genes specifically in the C. elegans germline. Upon closer analysis, we found that two rrf-1 mutants carrying different loss-of-function alleles were capable of processing RNAi targeting several somatically expressed genes. Specifically, we observed that the intestine was able to process RNAi triggers efficiently, whereas cells in the hypodermis showed partial susceptibility to RNAi in rrf-1 mutants. Other somatic tissues in rrf-1 mutants, such as the muscles and the somatic gonad, appeared resistant to RNAi. In addition to these observations, we found that the rrf-1(pk1417) mutation induced the expression of several transgenic arrays, including the FOXO transcription factor DAF-16. Unexpectedly, rrf-1(pk1417) mutants showed increased endogenous expression of the DAF-16 target gene sod-3; however, the lifespan and thermo-tolerance of rrf-1(pk1417) mutants were similar to those of wild-type animals. In sum, these data show that rrf-1 mutants display several phenotypes not previously appreciated, including broader tissue-specific RNAi-processing capabilities, and our results underscore the need for careful characterization of tissue-specific RNAi tools.

Structural features and bioavailability of four flavonoids and their implications for lifespan-extending and antioxidant actions in C. elegans

Various studies have demonstrated longevity effects of flavonoids, a major sub-group of plant polyphenolic compounds, in Caenorhabditis elegans. To better understand their structure–activity relationship in vivo we have used a comparative approach by exposing C. elegans to the structurally related flavonoids myricetin, quercetin, kaempferol and naringenin, and assessed their impact on lifespan and on putative modes of action. The bioavailability of the tested flavonoids was demonstrated by high-performance liquid chromatography with diode-array detection (HPLC/DAD) and a 2-aminoethyl diphenyl borate-based in vivo approach. While all flavonols increased lifespan in wild-type, only myricetin elongated the mev-1(kn1) lifespan, suggesting that the flavonols antioxidant action alone is not sufficient for longevity. Structural prerequisites of high antioxidant action in vitro were also essential to reduce the reactive oxygen species (ROS) load in vivo in C. elegans and were tested in isolated mouse muscle mitochondria. Since the insulin/IGF-like signaling (IIS) cascade is a key regulator of lifespan, all compounds were tested for the ability to cause nuclear translocation of the FOXO transcription factor DAF-16 and changes in target gene expression. An increased DAF-16 translocation and sod-3 promoter activity were observed with all flavonoids but was independent of their ROS scavenging capability and their effects on lifespan.

Monascin from red mold dioscorea as a novel antidiabetic and antioxidative stress agent in rats and Caenorhabditis elegans

Monascin is a major yellow compound from red mold dioscorea. We investigated monascin to test whether this compound acts as an antidiabetic and antioxidative stress agent in diabetic rats and Caenorhabditis elegans. The mechanisms by which monascin exerts its action in vivo were also examined. Streptozotocin (STZ)-induced diabetic rats were given monascin at 30mg/kg/day and sacrificed after 8weeks. Blood glucose and serum insulin, triglyceride, total cholesterol, and high-density lipoprotein and antioxidative enzymes in the pancreas of rats were measured. In addition, monascin was evaluated for stress resistance and potential associated mechanisms in C. elegans. Throughout the 8-week experimental period, significantly lowered blood glucose, serum triglyceride, and total cholesterol and higher high-density lipoprotein levels were observed in monascin-treated rats. Monascin-treated rats showed higher serum insulin level, lower reactive oxygen species production, and higher activities of glutathione peroxidase, superoxide dismutase, and catalase in the pancreas compared to diabetic control rats. In addition, monascin significantly induced the hepatic mRNA levels of FOXO3a, FOXO1, MnSOD, and catalase in STZ-induced diabetic rats. Monascin-treated C. elegans showed an increased survival rate during oxidative stress and heat stress treatments compared to untreated controls. Moreover, monascin extended the life span under high-glucose conditions and enhanced expression of small heat shock protein (sHSP-16.2), superoxide dismutase (SOD-3), and glutathione S-transferase (GST-4) in C. elegans. Finally, we showed that monascin affected the subcellular distribution of the FOXO transcription factor DAF-16, whereas it was unable to enhance oxidative stress resistance in the daf-16 deletion mutant in C. elegans. Mechanistic studies in rats and C. elegans suggest that the protective effects of monascin are mediated via regulation of the FOXO/DAF-16-dependent insulin signaling pathway by inducing the expression of stress response/antioxidant genes, thereby enhancing oxidative stress resistance.

Lifespan-Extending Effects of Royal Jelly and Its Related Substances on the Nematode Caenorhabditis elegans

BackgroundOne of the most important challenges in the study of aging is to discover compounds with longevity-promoting activities and to unravel their underlying mechanisms. Royal jelly (RJ) has been reported to possess diverse beneficial properties. Furthermore, protease-treated RJ (pRJ) has additional pharmacological activities. Exactly how RJ and pRJ exert these effects and which of their components are responsible for these effects are largely unknown. The evolutionarily conserved mechanisms that control longevity have been indicated. The purpose of the present study was to determine whether RJ and its related substances exert a lifespan-extending function in the nematode Caenorhabditis elegans and to gain insights into the active agents in RJ and their mechanism of action.Principal FindingsWe found that both RJ and pRJ extended the lifespan of C. elegans. The lifespan-extending activity of pRJ was enhanced by Octadecyl-silica column chromatography (pRJ-Fraction 5). pRJ-Fr.5 increased the animals' lifespan in part by acting through the FOXO transcription factor DAF-16, the activation of which is known to promote longevity in C. elegans by reducing insulin/IGF-1 signaling (IIS). pRJ-Fr.5 reduced the expression of ins-9, one of the insulin-like peptide genes. Moreover, pRJ-Fr.5 and reduced IIS shared some common features in terms of their effects on gene expression, such as the up-regulation of dod-3 and the down-regulation of dod-19, dao-4 and fkb-4. 10-Hydroxy-2-decenoic acid (10-HDA), which was present at high concentrations in pRJ-Fr.5, increased lifespan independently of DAF-16 activity.Conclusions/SignificanceThese results demonstrate that RJ and its related substances extend lifespan in C. elegans, suggesting that RJ may contain longevity-promoting factors. Further analysis and characterization of the lifespan-extending agents in RJ and pRJ may broaden our understanding of the gene network involved in longevity regulation in diverse species and may lead to the development of nutraceutical interventions in the aging process.

HIF‐1 modulates longevity and healthspan in a temperature‐dependent manner

The hypoxia-inducible factor HIF-1 has recently been identified as an important modifier of longevity in the roundworm Caenorhabditis elegans. Studies have reported that HIF-1 can function as both a positive and negative regulator of life span, and several disparate models have been proposed for the role of HIF in aging. Here, we resolve many of the apparent discrepancies between these studies. We find that stabilization of HIF-1 increases life span robustly under all conditions tested; however, deletion of hif-1 increases life span in a temperature-dependent manner. Animals lacking HIF-1 are long lived at 25°C but not at 15°C. We further report that deletion or RNAi knockdown of hif-1 impairs healthspan at lower temperatures because of an age-dependent loss of vulval integrity. Deletion of hif-1 extends life span modestly at 20°C when animals displaying the vulval integrity defect are censored from the experimental data, but fails to extend life span if these animals are included. Knockdown of hif-1 results in nuclear relocalization of the FOXO transcription factor DAF-16, and DAF-16 is required for life span extension from deletion of hif-1 at all temperatures regardless of censoring.

EAK proteins: novel conserved regulators of C. elegans lifespan

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.

Intracellular protein glycosylation modulates insulin mediated lifespan in C. elegans

O-linked-β-N-acetylglucosamine (O-GlcNAc) modification is a regulatory, nuclear and cytoplasmic post-translational glycosylation of proteins associated with age-related diseases such as Alzheimer's, Parkinson's, and type II diabetes. Global elevation of O-GlcNAc levels on intracellular proteins can induce insulin resistance, the hallmark of type II diabetes, in mammalian systems. InC. elegans, attenuation of the insulin-like signal transduction pathway increases adult lifespan of the nematode. We demonstrate that the O-GlcNAc cycling enzymes OGT and OGA, which add and remove O-GlcNAc respectively, modulate lifespan in C. elegans. Median adult lifespan is increased in an oga-1 deletion strain while median adult life span is decreased upon ogt-1 deletion. The O-GlcNAc-mediated effect on nematode lifespan is dependent on the FoxO transcription factor DAF-16. DAF-16 is a key factor in the insulin-like signal transduction pathway to regulate reproductive development, lifespan, stress tolerance, and dauer formation in C. elegans. Our data indicates that O-GlcNAc cycling selectively influences only a subset of DAF-16 mediated phenotypes, including lifespan and oxidative stress resistance. We performed an affinity purification of O-GlcNAc-modified proteins and observed that a high percentage of these proteins are regulated by insulin signaling and/or impact insulin pathway functional outcomes, suggesting that the O-GlcNAc modification may control downstream effectors to modulate insulin pathway mediated cellular processes.

CeKlotho opens a new road for investigation in worm aging

CeKlotho opens a new road for investigation in worm aging

The Somatic Reproductive Tissues of C. elegans Promote Longevity through Steroid Hormone Signaling

Author SummaryReproductive tissues are known to generate important intercellular signals. For example, in mammals, the reproductive tissues produce steroid hormones such as estrogen and testosterone that have profound effects on development and physiology. Studies of the nematode C. elegans and other organisms have shown that the reproductive system can also affect the rate at which an animal ages. Removal of C. elegans' germ cells extends lifespan but this effect is not simply due to sterility, as removal of both the somatic reproductive tissues and the germ cells does not extend lifespan. Instead, loss of the germ cells extends lifespan by activating a pathway that requires input from the somatic gonad. In this study, we demonstrate that the somatic reproductive tissues promote longevity by controlling the activity of a steroid signaling pathway that regulates the DAF-12 nuclear hormone receptor.

A pathway that links reproductive status to lifespan in Caenorhabditis elegans

In the nematode Caenorhabditis elegans and the fruit fly Drosophila, loss of the germline stem cells activates lifespan-extending FOXO-family transcription factors in somatic tissues and extends lifespan, suggesting the existence of an evolutionarily conserved pathway that links reproductive state and aging. Consistent with this idea, reproductive tissues have been shown to influence the lifespans of mice and humans as well. In C. elegans, loss of the germ cells activates a pathway that triggers nuclear localization of the FOXO transcription factor DAF-16 in endodermal tissue. DAF-16 then acts in the endoderm to activate downstream lifespan-extending genes. DAF-16 is also required for inhibition of insulin/insulin-like growth factor 1 (IGF-1) signaling to extend lifespan. However, the mechanisms by which inhibition of insulin/IGF-1 signaling and germline loss activate DAF-16/FOXO are distinct. As loss of the germ cells further doubles the already-long lifespan of insulin/IGF-1 pathway mutants, a better understanding of this reproductive longevity pathway could potentially suggest powerful ways to increase healthy lifespan in humans.

C. elegans germline-deficient mutants respond to pathogen infection using shared and distinct mechanisms.

Reproduction extracts a cost in resources that organisms are then unable to utilize to deal with a multitude of environmental stressors. In the nematode C. elegans, development of the germline shortens the lifespan of the animal and increases its susceptibility to microbial pathogens. Prior studies have demonstrated germline-deficient nematodes to have increased resistance to Gram negative bacteria. We show that germline-deficient strains display increased resistance across a broad range of pathogens including Gram positive and Gram negative bacteria, and the fungal pathogen Cryptococcus neoformans. Furthermore, we show that the FOXO transcription factor DAF-16, which regulates longevity and immunity in C. elegans, appears to be crucial for maintaining longevity in both wild-type and germline-deficient backgrounds. Our studies indicate that germline-deficient mutants glp-1 and glp-4 respond to pathogen infection using common and different mechanisms that involve the activation of DAF-16.

EAK-7 Controls Development and Life Span by Regulating Nuclear DAF-16/FoxO Activity

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.

Functional divergence of dafachronic acid pathways in the control of C. elegans development and lifespan

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 Δ4- and Δ7-dafachronic acid (DA) promote bypass of the dauer diapause and proper gonadal migration during larval development; in adults, DAs influence lifespan. Whether Δ4- and Δ7-DA have unique biological functions is not known. We identified the 3-β-hydroxysteroid dehydrogenase (3βHSD) family member HSD-1, which participates in Δ4-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 Δ7-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 Δ4- and Δ7-DA pathways have unique as well as overlapping biological functions in the control of development and lifespan.

Regulation of DAF-16-mediated Innate Immunity in Caenorhabditis elegans

Activation of the innate immune system results in a rapid microbicidal response against microorganisms, which needs to be fine-tuned because uncontrolled immune responses can lead to infection and cancer, as well as conditions such as Crohn disease, atherosclerosis, and Alzheimer disease. Here we report that excessive activity of the conserved FOXO transcription factor DAF-16 enhances susceptibility to bacterial infections in Caenorhabditis elegans. We found that increased temperature activates not only DAF-16 nuclear import but also a control mechanism involved in DAF-16 nuclear export. The nuclear export of DAF-16 requires heat shock transcription factor HSF-1 and Hsp70/HSP-1. Furthermore, we show that increased expression of the water channel Aquoporin-1 is responsible for the deleterious consequences of excessive DAF-16-mediated immune response. These studies reveal a stress-inducible mechanism involved in the regulation of DAF-16 and indicate that uncontrolled DAF-16 activity and water homeostasis are a cause of the deleterious effects of excessive immune responses.

Divergent Mechanisms Controlling Hypoxic Sensitivity and Lifespan by the DAF-2/Insulin/IGF-Receptor Pathway

Organisms and their cells vary greatly in their tolerance of low oxygen environments (hypoxia). A delineation of the determinants of hypoxia tolerance is incomplete, despite intense interest for its implications in diseases such as stroke and myocardial infarction. The insulin/IGF-1 receptor (IGFR) signaling pathway controls survival of Caenorhabditis elegans from a variety of stressors including aging, hyperthermia, and hypoxia. daf-2 encodes a C. elegans IGFR homolog whose primary signaling pathway modulates the activity of the FOXO transcription factor DAF-16. DAF-16 regulates the transcription of a large number of genes, some of which have been shown to control aging. To identify genes that selectively regulate hypoxic sensitivity, we compared the whole-organismal transcriptomes of three daf-2 reduction-of-function alleles, all of which are hypoxia resistant, thermotolerant, and long lived, but differ in their rank of severities for these phenotypes. The transcript levels of 172 genes were increased in the most hypoxia resistant daf-2 allele, e1370, relative to the other alleles whereas transcripts from only 10 genes were decreased in abundance. RNAi knockdown of 6 of the 10 genes produced a significant increase in organismal survival after hypoxic exposure as would be expected if down regulation of these genes by the e1370 mutation was responsible for hypoxia resistance. However, RNAi knockdown of these genes did not prolong lifespan. These genes definitively separate the mechanisms of hypoxic sensitivity and lifespan and identify biological strategies to survive hypoxic injury.

A conserved ubiquitination pathway determines longevity in response to diet restriction

Dietary restriction extends longevity in diverse species, suggesting that there is a conserved mechanism for nutrient regulation and prosurvival responses. Here we show a role for the HECT (homologous to E6AP carboxy terminus) E3 ubiquitin ligase WWP-1 as a positive regulator of lifespan in Caenorhabditis elegans in response to dietary restriction. We find that overexpression of wwp-1 in worms extends lifespan by up to 20% under conditions of ad libitum feeding. This extension is dependent on the FOXA transcription factor pha-4, and independent of the FOXO transcription factor daf-16. Reduction of wwp-1 completely suppresses the extended longevity of diet-restricted animals. However, the loss of wwp-1 does not affect the long lifespan of animals with compromised mitochondrial function or reduced insulin/IGF-1 signalling. Overexpression of a mutant form of WWP-1 lacking catalytic activity suppresses the increased lifespan of diet-restricted animals, indicating that WWP-1 ubiquitin ligase activity is essential for longevity. Furthermore, we find that the E2 ubiquitin conjugating enzyme, UBC-18, is essential and specific for diet-restriction-induced longevity. UBC-18 interacts with WWP-1 and is required for the ubiquitin ligase activity of WWP-1 and the extended longevity of worms overexpressing wwp-1. Taken together, our results indicate that WWP-1 and UBC-18 function to ubiquitinate substrates that regulate diet-restriction-induced longevity.

Rictor/TORC2 Regulates Caenorhabditis elegans Fat Storage, Body Size, and Development through sgk-1

The target of rapamycin (TOR) kinase coordinately regulates fundamental metabolic and cellular processes to support growth, proliferation, survival, and differentiation, and consequently it has been proposed as a therapeutic target for the treatment of cancer, metabolic disease, and aging. The TOR kinase is found in two biochemically and functionally distinct complexes, termed TORC1 and TORC2. Aided by the compound rapamycin, which specifically inhibits TORC1, the role of TORC1 in regulating translation and cellular growth has been extensively studied. The physiological roles of TORC2 have remained largely elusive due to the lack of pharmacological inhibitors and its genetic lethality in mammals. Among potential targets of TORC2, the pro-survival kinase AKT has garnered much attention. Within the context of intact animals, however, the physiological consequences of phosphorylation of AKT by TORC2 remain poorly understood. Here we describe viable loss-of-function mutants in the Caenorhabditis elegans homolog of the TORC2-specific component, Rictor (CeRictor). These mutants display a mild developmental delay and decreased body size, but have increased lipid storage. These functions of CeRictor are not mediated through the regulation of AKT kinases or their major downstream target, the insulin-regulated FOXO transcription factor DAF-16. We found that loss of sgk-1, a homolog of the serum- and glucocorticoid-induced kinase, mimics the developmental, growth, and metabolic phenotypes of CeRictor mutants, while a novel, gain-of-function mutation in sgk-1 suppresses these phenotypes, indicating that SGK-1 is a mediator of CeRictor activity. These findings identify new physiological roles for TORC2, mediated by SGK, in regulation of C. elegans lipid accumulation and growth, and they challenge the notion that AKT is the primary effector of TORC2 function.

Pseudomonas aeruginosa Suppresses Host Immunity by Activating the DAF-2 Insulin-Like Signaling Pathway in Caenorhabditis elegans

Some pathogens have evolved mechanisms to overcome host immune defenses by inhibiting host defense signaling pathways and suppressing the expression of host defense effectors. We present evidence that Pseudomonas aeruginosa is able to suppress the expression of a subset of immune defense genes in the animal host Caenorhabditis elegans by activating the DAF-2/DAF-16 insulin-like signaling pathway. The DAF-2/DAF-16 pathway is important for the regulation of many aspects of organismal physiology, including metabolism, stress response, longevity, and immune function. We show that intestinal expression of DAF-16 is required for resistance to P. aeruginosa and that the suppression of immune defense genes is dependent on the insulin-like receptor DAF-2 and the FOXO transcription factor DAF-16. By visualizing the subcellular localization of DAF-16::GFP fusion protein in live animals during infection, we show that P. aeruginosa–mediated downregulation of a subset of immune genes is associated with the ability to translocate DAF-16 from the nuclei of intestinal cells. Suppression of DAF-16 is mediated by an insulin-like peptide, INS-7, which functions upstream of DAF-2. Both the inhibition of DAF-16 and downregulation of DAF-16–regulated genes, such as thn-2, lys-7, and spp-1, require the P. aeruginosa two-component response regulator GacA and the quorum-sensing regulators LasR and RhlR and are not observed during infection with Salmonella typhimurium or Enterococcus faecalis. Our results reveal a new mechanism by which P. aeruginosa suppresses host immune defense.