Jeong, Dae-Eun et al. (2013) International Worm Meeting "Genes that influence longevity, dauer formation and pathogen responses downstream of sensory neurons in C. elegans."

Jeong, Dae-Eun, Gaglia, Marta M., Lee, Dongyeop, Kenyon, Cynthia, Lee, Seung-Jae, Ryu, Eun-A

[International Worm Meeting, 2013]

Sensory neurons of C. elegans affect the decision between arrest in the dauer stage and reproductive growth during larval development, and modulate the lifespan of the animals in adulthood. However, the molecular mechanisms by which sensory neurons influence these physiological processes are incompletely understood. Here we determined how different genes act downstream of sensory neurons to influence three physiological outputs - longevity, dauer formation and pathogen responses. Through genome-wide microarray analysis, we identified transcripts whose levels were influenced by mutations in the intraflagellar transport protein daf-10, which perturb morphology and function of many ciliated sensory neurons in C. elegans. First, among the genes with increased expression levels in daf-10 mutant animals, we identified a novel longevity factor, mct-1/2 (monocarboxylate transporter 1/2). mct-1/2 is predicted to transport small metabolites or hormones in the body, and we found that mct-1/2 was expressed in the pharyngeal tissue. Importantly, we demonstrated that mct-1/2 was required for the longevity of daf-10 mutants and was sufficient for increasing lifespan. Second, we found that a subset of genes whose levels were altered by daf-10 mutations are transcriptional targets of the DAF-12/nuclear hormone receptor. We showed that DAF-12/NHR specifically influenced the high-temperature-induced dauer-formation phenotype of daf-10 mutants, but did not affect their extended lifespan. Third, we found that several pathogen-responsive genes were repressed in daf-10 mutant animals. We found that daf-10 sensory mutants exhibited altered susceptibility to and behavioral avoidance of the bacterial pathogen, P. aeruginosa (PA14). Taken together, sensory input seems to influence the expression of diverse downstream genes that modulate basic biological processes in C. elegans.

Jeong, Dae-Eun et al. (2015) International Worm Meeting "Mitochondrial chaperone HSP-60 confers the anti-bacterial immunity via upregulating PMK-1 signaling in C. elegans."

Artan, Murat, Seo, Mihwa, Lee, Yujin, Seo, Keunhee, Hwang, Ara B., Oh, Young-Min, Lee, Seung-Jae V., Hwang, Wooseon, Hwang, Sun-Young, Baek, Haeshim, Jeong, Dae-Eun, Yoo, Joo-Yeon, Lee, Dongyeop, Son, Heehwa G.

[International Worm Meeting, 2015]

Recent studies have shown that mitochondria play key roles in mammalian immunity. C. elegans mitochondria also modulate resistance against pathogenic bacterial infection [1-4], suggesting a conserved role of mitochondria in immunity. However, specific mitochondrial components that regulate immunity at the organismal level remain largely unknown. Here, we identified mitochondrial proteins crucial for immunity by using C. elegans and P. aeruginosa (PA14) as an in vivo host-pathogen model. We performed an RNAi screen targeting 313 genes that encode evolutionarily conserved mitochondrial proteins. We identified 16 genes that reproducibly altered the survival of C. elegans upon PA14 infection. Among them, hsp-60, a major mitochondria-protective chaperone, was necessary and sufficient for enhancing resistance upon PA14 infection. We showed that intestine- or neuron-specific hsp-60 knockdown increased the susceptibility of animals to PA14. Genetic inhibition of the upstream regulators of HSP-60, including dve-1, ubl-5 or atfs-1, reduced the survival of worms upon PA14 infection but haf-1 mutation did not. We then determined the interaction between HSP-60 and PMK-1/p38 MAP kinase signaling, a key anti-bacterial immune pathway in C. elegans [5]. We showed that knockdown and overexpression of hsp-60 down- and up-regulated PMK-1, respectively. dve-1 and ubl-5 RNAi down-regulated PMK-1 signaling as well, whereas atfs-1 or haf-1 mutations did not. pmk-1 mutations largely suppressed the resistance to PA14 conferred by hsp-60 overexpression. These data suggest that the DVE-1/UBL-5/HSP-60 axis of mitochondrial chaperone function confers immunity via modulating PMK-1 signaling. Our data imply that HSP-60 may exert immune function by relaying signals from mitochondria to cytosolic p38 MAP kinase. [1] Hwang et al., 2014, PNAS, [2] Liu et al., 2014, Nature, [3] Pellegrino et al., 2014, Nature, [4] Kirienko et al., 2015, PNAS, [5] Kim et al., 2002, Science.

Lee, Dongyeop et al. (2011) International Worm Meeting "Identification of glucose-regulatory genes using a genome-wide RNAi screen."

Jeong, Dae-Eun, Lee, Seung-Jae, Lee, Dongyeop

[International Worm Meeting, 2011]

Glucose is an essential nutrient. The glucose metabolism should be tightly regulated and inappropriate regulation can cause diseases such as obesity, type 2 diabetes, and cardiovascular diseases. Recently, several studies reported that glucose directly shortens the life span of C. elegans (1, 2, 3). We showed that glucose shortens life span by down-regulating DAF-16/FOXO and HSF-1/heat shock factor 1, which are the life span-extending transcription factors downstream of insulin/IGF-1 signaling pathway (3). In addition, we identified glucose-responsive genes through microarray analysis and found that reduced expression of aqp-1/glycerol channel was responsible for the shortened life span (3). To further elucidate molecular mechanisms by which glucose affects life span, we plan to identify and to characterize glucose-regulatory genes by performing a genome-wide RNAi screen. We are using glucose-responsive GFP transgenic animals as a reporter for the screen. We examined other possible causes of the GFP induction and validated that the reporter is suitable for the RNAi screen. Through this genome-wide RNAi screen, we expect to find glucose-regulatory genes that may modulate life span under glucose-enriched condition and/or genes that may regulate glucose metabolism. This study will lead to better understanding of how glucose influences aging and metabolism at the molecular level. (1) Schulz et al., 2007, Cell Metabolism (2) Schlotterer et al., 2009, Diabetes (3) Lee et al., 2009, Cell Metabolism.

Antebi A (2005) Cell Metab "The prepared mind of the worm."

Antebi A

[Cell Metab, 2005]

In C. elegans, dauer pheromone is an indicator of population density and influences pathways that regulate metabolism, development, and aging. In a recent publication in Nature, Paik and coworkers (Jeong et al., 2005) show the purified substance to be a pyran ring conjugated to heptanoic acid, setting the stage for dissecting downstream signaling pathways.

Artan, Murat et al. (2013) International Worm Meeting "Sensory neuronal regulation of lifespan through modulating insulin-like peptides in C. elegans."

Jeong, Dae-Eun, Artan, Murat, Lee, Seung-Jae, Kim, Young-Il, Alcedo, Joy, Lee, Dongyeop

[International Worm Meeting, 2013]

Sensory neurons regulate the lifespan of several organisms, including C. elegans and Drosophila. In C. elegans, insulin/IGF-1 and steroid signaling pathways have been shown to mediate the longevity response by sensory neurons. Although it is established that perturbation of chemosensory neurons promotes longevity by activating DAF-16, upstream mediators of this activation are poorly understood. Here, we show that mutations in tax-2 and tax-4, which encode subunits of neural cGMP-gated channels, increase lifespan at low temperature via modulating the expression of several insulin-like peptides. After confirming daf-16-dependency of longevity by tax-2 mutations, we determined the tissues crucial for the action of DAF-16. We found that pan-neuronal, intestinal or hypodermal expression of DAF-16::GFP partially rescued the short lifespan of tax-2 daf-16 double mutants, whereas muscle-specific expression did not. In addition, tax-2 mutations increased nuclear localization of DAF-16 in non-neuronal tissues, including the intestine. Because the expression of tax-2 and tax-4 is restricted to neurons, these data suggest a tissue non-autonomous signaling between sensory neurons and other tissues. In addition, the expression of sod-3, dod-8 and mtl-1, downstream target genes of DAF-16, was elevated in tax-2; tax-4 mutants, suggesting a transcriptional activation of DAF-16. Next, we reasoned that neuroendocrine signaling via insulin-like peptides may participate in the longevity of tax-2 and tax-4 mutants. Among 34 insulin-like peptide genes we examined, daf-28 and ins-6 were significantly repressed in tax-2; tax-4 mutants. We demonstrated the functional significance of this down-regulation by showing that overexpression of ins-6 or daf-28 suppressed the long lifespan of tax-2 mutants. Together, we propose that sensory neurons modulate lifespan via neuroendocrine signaling mediated by insulin-like peptides that regulate the activity of DAF-16.

Seo, Keunhee et al. (2013) International Worm Meeting "Mutations in ribosomal S6 kinase lengthen lifespan through increasing the activity of heat shock transcription factor 1."

Seo, Keunhee, Jang, Sung Key, Lee, Dongyeop, Lee, Seung-Jae, Jeong, Dae-Eun, Choi, Eunseok

[International Worm Meeting, 2013]

It has been established that aging is subject to regulation by classical signaling pathways, including insulin/IGF-1 signaling (IIS) and target of rapamycin (TOR) signaling. The TOR signaling pathway has emerged as a major regulator of aging, and one of the well-characterized effectors of TOR signaling is ribosomal protein S6 kinase whose inhibition increases the lifespan of yeast, C. elegans, Drosophila and mice. Here, we show that inhibition of S6 kinase (rsks-1) exerts lifespan-extending effects on C. elegans via increasing the activity of the heat shock transcription factor 1 (HSF-1), a crucial longevity transcription factor known to act downstream of the IIS pathway. We initially noticed that hsf-1 genetically interacted with rsks-1 through a genome-wide RNAi screen. We then found that hsf-1 was required for the extended life span of rsks-1 mutants. In addition, inhibition of hsf-1 suppressed the longevity caused by the reduction of other components in the TOR signaling pathway, including raptor (daf-15), Rag GTPase (ragc-1) and ribosomal protein subunits (rps-6 and rps-15). Moreover, we found that hsf-1 was required for the enhanced resistance of rsks-1 mutants against oxidative stress, protein aggregation, and pathogenic P. aeruginosa (PA14). Since HSF-1 is a longevity transcription factor crucial for the induction of various chaperone genes, we examined whether rsks-1 mutations increased the mRNA levels of several HSF-1 target genes. Among them, hsp-16 and hsp-70 were induced by rsks-1 mutations, and hsp-16 was at least partially required for the longevity of rsks-1 mutants. We then asked whether HSF-1 acts as a downstream longevity factor for both IIS and TOR signaling. We found that the enhanced longevity of rsks-1; daf-2 double mutants was mediated by HSF-1. Together, our findings suggest that HSF-1 functions as a hub transcription factor that integrates longevity signals from IIS and TOR/S6K pathways.

Lee, Yujin et al. (2019) International Worm Meeting "DAF-16/FOXO and HSF-1 rejuvenate immunity via an INS-7-mediated positive feedback loop in daf-2 mutants."

Hwang, Wooseon, Park, Hae-Eun, Ashraf, Jasmine, Lee, Yujin, Murphy, Coleen, Lee, Seung-Jae, Kwon, Sujeong, Jeong, Dae-Eun, Jung, Yoonji

[International Worm Meeting, 2019]

A hallmark of aging is immunosenescence, a gradual age-dependent deterioration of immune functions. Immunosenescence seems to be inevitable in most organisms. Here, we determined the roles of DAF-2/insulin/IGF-1 receptor signaling in immunosenescence by using C. elegans and P. aeruginosa (PA14) as a host and a bacterial pathogen, respectively. Surprisingly, we found that daf-2/insulin/IGF-1 receptor mutations or daf-2 RNAi significantly delayed immunosenescence and even rejuvenated immunity in old age. We showed that temporal RNAi knock down of daf-2 was sufficient to reverse immunosenescence. We found that two longevity transcription factors, DAF-16/FOXO and heat-shock factor 1 (HSF-1), were required for the improved immunocompetence in old daf-2(e1370) mutants. In contrast, p38 mitogen-activated protein kinase (PMK-1) cascade signaling, a major determinant of immunosenescence in wild-type [1], was dispensable for the enhanced immunocompetence in old daf-2 mutants. Through performing RNA seq. analysis, we showed that the expression of ins-7, an agonistic insulin-like peptide that was negatively regulated by both DAF-16 and HSF-1, was up-regulated during aging in wild-type, but not in daf-2 mutants. Notably, ins-7 mutations increased immunocompetence in old age, indicating that ins-7 is a causal factor for immunosenescence. From a targeted genetic screen, we then identified ZIP-10/bZIP transcription factor as a positive regulator of ins-7 in old worms and showed that mutations in zip-10 enhanced immunocompetence in old age. Thus, daf-2 mutations appear to activate DAF-16 and HSF-1, while inactivating ZIP-10 with age. This in turn down-regulates INS-7, leading to further reduction of DAF-2 signaling. This whole positive feedback endocrine circuit appears to reverse immunosenescence in daf-2 mutants. Because IIS is highly conserved across phyla, our study may eventually help developing strategies for immune rejuvenation in humans. [1] Youngman, M. J., Rogers, Z. N., & Kim, D. H. (2011). A decline in p38 MAPK signaling underlies immunosenescence in Caenorhabditis elegans. PLoS genetics, 7(5), e1002082.

Mari Ohtani et al. (2007) International Worm Meeting "Lifespan extending activity of C. elegans secreta."

Shuji Honda, Mari Ohtani, Yasuo Kimura, Yoko Honda, Tsuyoshi Kawano

[International Worm Meeting, 2007]

In a response to unfavorable growth conditions such as overpopulation and lack of adequate diet, C. elegans ceases development and enters a growth-arrested stage, a kind of larval diapause. The substance that induces the diapause is yielded by the animal and is called dauer-inducing pheromone. The animal uses the pheromone as a chemical mediator to detect overcrowding. In 2005, Jeong and co-workers isolated daumone as a dauer-inducing pheromone and elucidated its structure.1) During our trial of isolating the pheromone, we found lifespan extending activity as well as diapause-inducing activity in a crude extract of C. elegans culture..2) To remove the daumone, the crude extract was subjected to anion-exchange chromatography. The resulting extract also induced an extended lifespan, suggesting that a substance(s) distinct from daumone has lifespan extending activity. The activity disappeared in a daf-16 mutant animal, indicating daf-16 dependency. We are going to check subcellular localization of DAF-16::GFP by the extract. 1) Jeong, P. Y., et al. (2005) Nature 433:541.2) Kawano, T., et al. (2005) Biosci. Biotechnol. Biochem. 69:2479.

Zhang, Peichuan et al. (2009) International Worm Meeting "Understanding tissue-specificity of DAF-16/FOXO activity in gene regulation and lifespan control."

Zhang, Peichuan, Kenyon, Cynthia

[International Worm Meeting, 2009]

In long-lived mutant animals with decreased insulin/IGF-1 signaling activity, expression of many longevity-associated genes requires the forkhead transcription factor DAF-16/FOXO [1]. In order to understand the regulatory mechanisms for longevity control by DAF-16/FOXO, we have analyzed how DAF-16/FOXO functions in animal''s tissues to control the expression of its downstream target genes. We have found that DAF-16/FOXO acts in a cell-autonomous fashion to up- or down-regulate many of its target genes in long-lived daf-2 mutant animals. In our analysis of dod-8, a target gene that is regulated cell autonomously by DAF-16/FOXO, we find that DAF-16/FOXO can bind to both DAF-16/FOXO-associated element (DAE) [1] and other non-canonical sub-optimal sites that are located within the dod-8 promoter. Moreover, the DAE site is essential for in vivo expression of dod-8 in daf-2 mutant animals. Interestingly, we have also found that nematode GATA factors also bind to the DAE site. We are currently addressing potential co-regulation of dod genes by DAF-16/FOXO and GATA factors. Long-lived animals with activation of DAF-16/FOXO only in the intestine display enhanced locomotion behavior at mid-age and increased lifespan [2]. In accordance with such benefits, we have found that intestinal DAF-16/FOXO activity acts cell non-autonomously to protect muscles that lack daf-16/foxo from the deterioration that accompanies normal aging. Thus, intestinal DAF-16 must regulate certain signaling pathway(s) that influence the rate of aging of other tissues. Using RFP fusions, we showed that intestinal DAF-16/FOXO can turn on expression of certain DAF-16-regulated genes in daf-16(-) tissues. Such cell non-autonomous regulation likely underlies the ability of intestinal DAF-16/FOXO to promote the survival of daf-16(-) tissues. We are currently analyzing candidate RNAi clones that perturb the cell non-autonomous gene regulation by DAF-16/FOXO to identify the downstream signaling pathway(s) that mediate tissue crosstalk and longevity control. Reference: 1)Murphy, C. et al. (2003) Genes that act downstream of DAF-16 to influence the lifespan of Caenorhabditis elegans. Nature 427:277-83. 2)Libina, N., Berman, J., and Kenyon, C. (2003) Tissue-specific activities of C. elegans DAF-16 in the regulation of lifespan. Cell 115:489-502.

Park, Sangsoon et al. (2021) International Worm Meeting "Diacetyl odor shortens food deprivation-induced longevity via downregulating DAF-16"

Artan, Murat, Son, Heehwa G., Jung, Yoonji, Kim, Sieun S., Park, Sangsoon, Lee, Jin I., Park, Hae-Eun H., Jeong, Dae-Eun, Choi, Yunji, Lee, Seung-Jae V., Kim, Kyuhyung

[International Worm Meeting, 2021]

Dietary restriction extends lifespan in multiple species by reducing nutrient intake and access to non-nutritional food-derived cues. The nutritional effects of dietary restriction on longevity has been extensively studied. However, the roles of food-derived sensory cues in longevity conferred by dietary restriction or the identity of specific food-derived chemical cues that alter lifespan remain unclear. Here, we sought to identify food-derived volatile sensory cues that regulate lifespan in C. elegans. We first determined the effects of seven selected bacteria-derived volatile attractants on lifespan under food deprivation, one of life-extending dietary restriction regimens in C. elegans. We found that the odor of diacetyl, 2,3-pentanedione, 2,4,5-trimethylthiazole, or benzaldehyde decreased the longevity conferred by food deprivation. We then tested whether the lifespan-reducing chemicals affected the activity of DAF-16, a longevity-promoting transcription factor acting downstream of sensory and insulin/IGF-1 signaling. We found that the odor of diacetyl or 2,3-pentanedione reduced the nuclear localization of DAF-16 under the food-deprived condition. We further showed that the diacetyl odor, which caused the greatest effect on the subcellular localization of DAF-16, reduced the expression of DAF-16-regulated genes, including sod-3, mtl-1, and hsp-12.6. These findings suggest that diacetyl reduces longevity conferred by food deprivation via downregulating DAF-16. Unexpectedly, we found that the odor of diacetyl decreased longevity caused by food deprivation in two established diacetyl receptor mutants, odr-10(ky225) and sri-14(ok2865) single and double mutants. Thus, diacetyl, a food-derived odorant, may shorten food deprivation-mediated longevity via downregulating DAF-16 by binding to unidentified receptors. We then examined whether diacetyl that is produced under physiological conditions regulated DAF-16 activity or lifespan. We found that the odor of diacetyl-producing lactic acid bacteria reduced the nuclear localization of DAF-16 under food deprivation but did not shorten longevity. These data suggest that the odor of diacetyl-producing lactic acid bacteria downregulates DAF-16 but is not sufficient to decrease lifespan in food-deprived conditions. Together, our study identified diacetyl as a longevity-reducing food-derived volatile sensory cue that downregulates DAF-16. Our study will provide valuable insights into mechanisms by which reduced food odors contribute to dietary restriction-mediated longevity via sensory signaling.