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FOXO and HSF1 rejuvenate immunity via positive feedback regulation of insulin/IGF-1 signaling

ABSTRACT: A hallmark of aging is immunosenescence, a decline in immune function that appeared to be inevitable. Surprisingly, here we show that genetic inhibition of DAF-2/insulin/IGF-1 receptor drastically delays immunosenescence and even rejuvenates immunity in C. elegans. We find that p38 mitogen activated protein kinase (PMK-1), a key determinant of immunosenescence in wild-type, is dispensable for this rejuvenated immunity. Instead, we demonstrate that longevity-promoting DAF-16/FOXO and heat-shock transcription factor 1 (HSF-1) increase immunocompetence in old daf-2(-) animals. The up-regulation of DAF-16/FOXO and HSF-1 decreases the expression of zip-10/bZip transcription factor, which in turn down-regulates ins-7, an agonistic insulin-like peptide, for further reduction in insulin/IGF-1 signaling (IIS). Thus, reduced IIS bypasses immunosenescence and rejuvenates immunity via up-regulating anti-aging transcription factors that regulate an endocrine insulin-like peptide through a positive feedback mechanism. Because many functions of IIS are conserved across phyla, our study may lead to developing strategies for immune rejuvenation in humans.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE137861 | GEO | 2021/02/26

REPOSITORIES: GEO

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Project description:Post-embryonic development of the nematode C. elegans is governed by nutrient availability. L1-stage larvae remain in a state of developmental arrest after hatching until they feed. This “L1 arrest” (or "L1 diapause") is associated with increased stress resistance, supporting starvation survival. Loss of the transcription factor daf-16/FOXO, an effector of insulin/IGF signaling, results in arrest-defective and starvation-sensitive phenotypes. We show that daf-16/FOXO regulates L1 arrest cell-nonautonomously, suggesting that insulin/IGF signaling regulates at least one additional signaling pathway. We used mRNA-seq to identify candidate signaling molecules affected by daf-16/FOXO during L1 arrest. daf-16/FOXO had overlapping but distinct effects on gene expression in L1 arrest compared to daf-2/InsR adults. Notably, dbl-1/TGF-β, a ligand for the Sma/Mab pathway, and daf-36, which encodes an upstream component of the daf-12/NHR steroid hormone signaling pathway, were up-regulated during L1 arrest in a daf-16/FOXO mutant. Using genetic epistasis analysis, we show that dbl-1/TGF-β and daf-12/NHR steroid hormone signaling pathways are required for the daf-16/FOXO arrest-defective phenotype, suggesting that daf-16/FOXO represses dbl-1/TGF-β and daf-36. The dbl-1/TGF-β and daf-12/NHR pathways have not previously been shown to affect L1 development, but we found that disruption of these pathways delayed L1 development in fed larvae, consistent with these pathways promoting development in starved daf-16/FOXO mutants. Though the dbl-1/TGF-β and daf-12/NHR pathways are epistatic to daf-16/FOXO for the arrest-defective phenotype, disruption of these pathways does not suppress starvation sensitivity of daf-16/FOXO mutants. This observation uncouples starvation survival from developmental arrest, indicating that DAF-16/FOXO targets distinct effectors for each phenotype, and revealing that inappropriate development during starvation does not cause the early demise of daf-16/FOXO mutants. Overall, this study shows that daf-16/FOXO promotes developmental arrest cell-nonautonomously by repressing pathways that promote larval development.

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FOXO and HSF1 rejuvenate immunity via positive feedback regulation of insulin/IGF-1 signaling

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