Inhibition of the master growth regulator mTORC1 (mechanistic target of rapamycin complex 1) slows ageing across phyla, in part by reducing protein synthesis. Various stresses globally suppress protein synthesis through the integrated stress response (ISR), resulting in preferential translation of the transcription factor ATF-4. Here we show in C. elegans that inhibition of translation or mTORC1 increases ATF-4 expression, and that ATF-4 mediates longevity under these conditions independently of ISR signalling. ATF-4 promotes longevity by activating canonical anti-ageing mechanisms, but also by elevating expression of the transsulfuration enzyme CTH-2 to increase hydrogen sulfide (H2S) production. This H2S boost increases protein persulfidation, a protective modification of redox-reactive cysteines. The ATF-4/CTH-2/H2S pathway also mediates longevity and increased stress resistance from mTORC1 suppression. Increasing H2S levels, or enhancing mechanisms that H2S influences through persulfidation, may represent promising strategies for mobilising therapeutic benefits of the ISR, translation suppression, or mTORC1 inhibition. 

https://www.nature.com/articles/s41467-022-28599-9.pdf

ATF-4 and hydrogen sulfide signalling mediate longevity in response to inhibition of translation or mTORC1

The aging process is characterized by a progressive decline in the function of most tissues, representing the main risk factor in the development of a variety of human diseases. Studies in multiple animal models have demonstrated that interventions that improve the capacity to maintain endoplasmic reticulum (ER) proteostasis prolong life and healthspan. ER stress is monitored by the unfolded protein response (UPR), a signaling pathway that mediates adaptive processes to restore proteostasis or the elimination of damaged cells by apoptosis. Here, we discuss recent advances in understanding the significance of the UPR to aging and its implications for the maintenance of cell physiology of various cell types and organs. The possible benefits of targeting the UPR to extend healthspan and reduce the risk of developing age-related diseases are also discussed.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/acel.13265

Mastering organismal aging through the endoplasmic reticulum proteostasis network.

The metabolome represents a complex network of biological events that reflects the physiologic state of the organism in heath and disease. Additionally, specific metabolites and metabolic signaling pathways have been shown to modulate animal ageing, but whether there are convergent mechanisms uniting these processes remains elusive. Here, we used high resolution mass spectrometry to obtain the metabolomic profiles of canonical longevity pathways in C. elegans and identify metabolites regulating life span. By leveraging the metabolomic profiles across pathways, we found that one carbon metabolism and the folate cycle were pervasively regulated in common. We observed similar changes in long lived mouse models of reduced insulin/IGF signaling. Genetic manipulation of pathway enzymes and supplementation with one carbon metabolites reveal that regulation of the folate cycle represents a shared causal mechanism of longevity and proteoprotection.

https://biorxiv.org/content/10.1101/2020.07.07.191544v1.full.pdf

Regulation of the one carbon folate cycle as a shared metabolic signature of longevity

/pdf/atf-4-and-hydrogen-sulfide-signalling-mediate-longevity-in-7xngoyj4.pdf

Sustaining a healthy proteome is a lifelong challenge for each individual cell of an organism. However, protein homeostasis or proteostasis is constantly jeopardized since damaged proteins accumulate under proteotoxic stress that originates from ever-changing metabolic, environmental, and pathological conditions. Proteostasis is achieved via a conserved network of quality control pathways that orchestrate the biogenesis of correctly folded proteins, prevent proteins from misfolding, and remove potentially harmful proteins by selective degradation. Nevertheless, the proteostasis network has a limited capacity and its collapse deteriorates cellular functionality and organismal viability, causing metabolic, oncological, or neurodegenerative disorders. While cell-autonomous quality control mechanisms have been described intensely, recent work on Caenorhabditis elegans has demonstrated the systemic coordination of proteostasis between distinct tissues of an organism. These findings indicate the existence of intricately balanced proteostasis networks important for integration and maintenance of the organismal proteome, opening a new door to define novel therapeutic targets for protein aggregation diseases. Here, we provide an overview of individual protein quality control pathways and the systemic coordination between central proteostatic nodes. We further provide insights into the dynamic regulation of cellular and organismal proteostasis mechanisms that integrate environmental and metabolic changes. The use of C. elegans as a model has pioneered our understanding of conserved quality control mechanisms important to safeguard the organismal proteome in health and disease.

https://www.genetics.org/content/genetics/215/4/889.full.pdf

Organismal Protein Homeostasis Mechanisms.

Mitochondria are multidimensional organelles whose activities are essential to cellular vitality and organismal longevity, yet underlying regulatory mechanisms spanning these different levels of organization remain elusive1–5. Here we show that Caenorhabditis elegans nuclear transcription factor Y, beta subunit (NFYB-1), a subunit of the NF-Y transcriptional complex6–8, is a crucial regulator of mitochondrial function. Identified in RNA interference (RNAi) screens, NFYB-1 loss leads to perturbed mitochondrial gene expression, reduced oxygen consumption, mitochondrial fragmentation, disruption of mitochondrial stress pathways, decreased mitochondrial cardiolipin levels and abolition of organismal longevity triggered by mitochondrial impairment. Multi-omics analysis reveals that NFYB-1 is a potent repressor of lysosomal prosaposin, a regulator of glycosphingolipid metabolism. Limiting prosaposin expression unexpectedly restores cardiolipin production, mitochondrial function and longevity in the nfyb-1 background. Similarly, cardiolipin supplementation rescues nfyb-1 phenotypes. These findings suggest that the NFYB-1–prosaposin axis coordinates lysosomal to mitochondria signalling via lipid pools to enhance cellular mitochondrial function and organismal health. Tharyan et al. identify NFYB-1 as a regulator of mitochondrial function that represses lysosomal prosaposin. The NFYB-1–prosaposin signalling axis coordinates lysosomal-to-mitochondria signalling via cardiolipin to enhance cellular mitochondrial function and longevity in C. elegans.

NFYB-1 regulates mitochondrial function and longevity via lysosomal prosaposin

Hexosamine Pathway Activation Improves Protein Homeostasis through the Integrated Stress Response

Muscle function relies on the precise architecture of dynamic contractile elements, which must be fine-tuned to maintain motility throughout life. Muscle is also plastic, and remodeled in response to stress, growth, neural and metabolic inputs. The conserved muscle-enriched microRNA, miR-1, regulates distinct aspects of muscle development, but whether it plays a role during aging is unknown. Here we investigated Caenorhabditis elegans miR-1 in muscle function in response to proteostatic stress. mir-1 deletion improved mid-life muscle motility, pharyngeal pumping, and organismal longevity upon polyQ35 proteotoxic challenge. We identified multiple vacuolar ATPase subunits as subject to miR-1 control, and the regulatory subunit vha-13/ATP6V1A as a direct target downregulated via its 3'UTR to mediate miR-1 physiology. miR-1 further regulates nuclear localization of lysosomal biogenesis factor HLH-30/TFEB and lysosomal acidification. Our studies reveal that miR-1 coordinately regulates lysosomal v-ATPase and biogenesis to impact muscle function and health during aging.

miR-1 coordinately regulates lysosomal v-ATPase and biogenesis to impact proteotoxicity and muscle function during aging.

Muscle function relies on the precise architecture of dynamic contractile elements, which must be fine-tuned to maintain motility throughout life. Muscle is also highly plastic, and remodelled in response to stress, growth, neural and metabolic inputs. The evolutionarily conserved muscle-enriched microRNA, miR-1, regulates distinct aspects of muscle biology during development, but whether it plays a role during ageing is unknown. Here we investigated the role of C. elegans miR-1 in muscle function in response to proteostatic stress during adulthood. mir-1 deletion results in improved mid-life muscle motility, pharyngeal pumping, and organismal longevity under conditions of polyglutamine repeat proteotoxic challenge. We identified multiple vacuolar ATPase subunits as subject to miR-1 control, and the regulatory subunit vha-13/ATP6VIA as a direct target downregulated via its 3’UTR to mediate miR-1 physiology. miR-1 further regulates nuclear localization of lysosomal biogenesis factor HLH-30/TFEB and lysosomal acidification. In summary, our studies reveal that miR-1 coordinately regulates lysosomal v-ATPase and biogenesis to impact muscle function and health during ageing.

/pdf/mir-1-coordinately-regulates-lysosomal-v-atpase-and-2an4jncr6a.pdf

Isabelle Schiffer

Papers

NFYB-1 regulates mitochondrial function and longevity via lysosomal prosaposin

Hexosamine Pathway Activation Improves Protein Homeostasis through the Integrated Stress Response

miR-1 coordinately regulates lysosomal v-ATPase and biogenesis to impact proteotoxicity and muscle function during aging.

miR-1 coordinately regulates lysosomal v-ATPase and biogenesis to affect muscle contractility upon proteotoxic challenge during ageing