Unfolded protein response (UPR) of the endoplasmic reticulum (UPRER) helps maintain proteostasis in the cell. The ability to mount an effective UPRER to external stress (iUPRER) decreases with age and is linked to the pathophysiology of multiple age-related disorders. Here, we show that a transient pharmacological ER stress, imposed early in development on Caenorhabditis elegans, enhances proteostasis, prevents iUPRER decline with age, and increases adult life span. Importantly, dietary restriction (DR), that has a conserved positive effect on life span, employs this mechanism of ER hormesis for longevity assurance. We found that only the IRE-1–XBP-1 branch of UPRER is required for the longevity effects, resulting in increased ER-associated degradation (ERAD) gene expression and degradation of ER resident proteins during DR. Further, both ER hormesis and DR protect against polyglutamine aggregation in an IRE-1–dependent manner. We show that the DR-specific FOXA transcription factor PHA-4 transcriptionally regulates the genes required for ER homeostasis and is required for ER preconditioning-induced life span extension. Finally, we show that ER hormesis improves proteostasis and viability in a mammalian cellular model of neurodegenerative disease. Together, our study identifies a mechanism by which DR offers its benefits and opens the possibility of using ER-targeted pharmacological interventions to mimic the prolongevity effects of DR.
Germ line integrity is critical for progeny fitness. Organisms deploy the DNA damage response (DDR) signaling to protect the germ line from genotoxic stress, facilitating the cell-cycle arrest of germ cells and DNA repair or their apoptosis. Cell-autonomous regulation of germ line quality in response to DNA damage is well-studied; however, how quality is enforced cell non-autonomously on sensing somatic D NA damage is less known. Using Caenorhabditis elegans, we show that DDR disruption, only in the uterus, when insulin-IGF-1 signaling (IIS) is low, arrests oogenesis in the pachytene stage of meiosis I, in a FOXO/DAF-16 transcription factor (TF)-dependent manner. Without FOXO/DAF-16, germ cells of the IIS mutant escape the arrest to produce poor-quality oocytes, showing that the TF imposes strict quality control during low IIS. Activated FOXO/DAF-16 senses DDR perturbations during low IIS to lower ERK/MPK-1 signaling below a threshold to promote germ line arrest. Altogether, we elucidate a new surveillance role of activated FOXO/DAF-16 that ensures optimal germ cell quality and progeny fitness in response to somatic DNA damage.
Germline integrity is critical for progeny fitness. Organisms deploy the DNA damage response (DDR) signalling to protect germline from genotoxic stress, facilitating cell-cycle arrest of germ cells and DNA repair or their apoptosis. Cell-autonomous regulation of germline quality is well-studied; however, how quality is enforced cell non-autonomously on sensing somatic DNA damage is less known. Using Caenorhabditis elegans, we show that DDR disruption, only in the uterus, when insulin-IGF-1 signalling (IIS) is low, arrests germline development and induces sterility in a FOXO/DAF-16 transcription factor (TF)-dependent manner. Without FOXO/DAF-16, germ cells of the IIS mutant escape arrest to produce poor quality oocytes, showing that the TF imposes strict quality control during low IIS. In response to low IIS in neurons, FOXO/DAF-16 works cell autonomously as well as non-autonomously to facilitate the arrest. Activated FOXO/DAF-16 promotes transcription of checkpoint and DDR genes, protecting germline integrity. However, on reducing DDR during low IIS, the TF decreases ERK/MPK-1 signaling below a threshold, and transcriptionally downregulates genes involved in spermatogenesis-to-oogenesis switch as well as cdk-1/Cyclin B to promote germline arrest. Altogether, our study reveals how cell non-autonomous function of FOXO/DAF-16 promotes germline quality and progeny fitness in response to somatic DNA damage.Significance StatementReproductive decisions are supervised processes that take into account various inputs like cellular energy availability and status of damage repair in order to ensure healthy progeny. In this study, we show that the absence of optimal DNA damage repair in the somatic uterine tissues prevents oocyte development by the cell-autonomous as well non-autonomous function of activated FOXO transcription factor DAF-16. Thus, this study elucidates a new surveillance role of FOXO/DAF-16 in somatic tissues that ensures progeny fitness.
Germline integrity is critical for progeny fitness. Organisms deploy the DNA damage response (DDR) signalling to protect germline from genotoxic stress, facilitating cell-cycle arrest of germ cells and DNA repair or their apoptosis. Cell-autonomous regulation of germline quality is well-studied; however, how quality is enforced cell non-autonomously on sensing somatic DNA damage is less known. Using Caenorhabditis elegans, we show that DDR disruption, only in the uterus, when insulin-IGF-1 signalling (IIS) is low, arrests germline development and induces sterility in a FOXO/DAF-16 transcription factor (TF)-dependent manner. Without FOXO/DAF-16, germ cells of the IIS mutant escape arrest to produce poor quality oocytes, showing that the TF imposes strict quality control during low IIS. In response to low IIS in neurons, FOXO/DAF-16 works cell autonomously as well as non-autonomously to facilitate the arrest. Activated FOXO/DAF-16 promotes transcription of checkpoint and DDR genes, protecting germline integrity. However, on reducing DDR during low IIS, the TF decreases ERK/MPK-1 signaling below a threshold, and transcriptionally downregulates genes involved in spermatogenesis-to-oogenesis switch as well as cdk-1/Cyclin B to promote germline arrest. Altogether, our study reveals how cell non-autonomous function of FOXO/DAF-16 promotes germline quality and progeny fitness in response to somatic DNA damage.
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