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Methods Mol Biol,
2006]
Whether by patch-clamp techniques or the use of fluorescent vital dyes, measurements of transepithelial ion flux in mammals are limited by cell accessibility. Furthermore, redundant functions and complex regulatory mechanisms can mask loss-of-function phenotypes through compensatory mechanisms. In this chapter, we present a technique whereby the optically transparent nematode Caenorhabditis elegans, engineered to express a fluorescent pH indicator protein, can be used to study how intracellular pH (pHi) fluctuates in response to environmental and/or experimental challenge. By using a live whole animal model, systemic, and even behavioral relationships to individual cellular pHi can be inferred. In combination with dye loading of excised or cultured cells, this technique also provides a powerful means of contrasting these relationships to biophysical measurements of ion flux.
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Curr Biol,
2003]
The DAF-16 transcription factor controls aging in C. elegans as part of an insulin-like signaling pathway. Identification of a target of DAF-16 has opened a new window into the aging process.
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Cell Cycle,
2006]
A conserved
sir2 deacetylase gene can determine longevity of yeast, flies and worms. Recently we have reported a molecular mechanism of action of the C. elegans homologue
sir-2.1. Our study revealed a novel stress-dependent pathway for lifespan determination in which SIR-2.1 binds to 14-3-3 proteins and a forkhead transcription factor DAF-16 to activate transcription of DAF-16 target genes. DAF-16 has long been known as a central protein in the regulation of lifespan that interfaces with multiple pathways. Recent studies by us and other laboratories suggest that DAF-16 requires co-factors for full activity. In this prospective we review recent literature highlighting the role of SIR-2.1, 14-3-3 and other DAF-16 co-factors in DAF-16 activation.
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Dev Dyn,
2010]
In a remarkably conserved insulin signaling pathway that is well-known for its regulation of longevity in worms, flies, and mammals, the major C. elegans effector of this pathway, DAF-16/FOXO, also modulates many other physiological processes. This raises the question of how DAF-16/FOXO chooses the correct targets to achieve the appropriate response in a particular context. Here, we review current knowledge of tissue-specificity and interacting partners that modulate DAF-16/FOXO functional output.
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Exp Gerontol,
2006]
In Caenorhabditis elegans, the insulin/IGF-1 signaling pathway controls many biological processes such as life span, fat storage, dauer diapause, reproduction and stress response . This pathway is comprised of many genes including the insulin/IGF-1 receptor (DAF-2) that signals through a conserved PI 3-kinase/AKT pathway and ultimately down-regulates DAF-16, a forkhead transcription factor (FOXO). DAF-16 also receives input from several other pathways that regulate life span such as the germline and the JNK pathway [Hsin, H., Kenyon, C., 1999. Signals from the reproductive system regulate the lifespan of C. elegans. Nature 399, 362-366; Oh, S.W., Mukhopadhyay, A., Svrzikapa, N., Jiang, F., Davis, R.J., Tissenbaum, H.A., 2005. JNK regulates lifespan in Caenorhabditis elegans by modulating nuclear translocation of forkhead transcription factor/DAF-16. Proc. Natl. Acad. Sci. USA 102, 4494-4499]. Therefore, DAF-16 integrates signals from multiple pathways and regulates its downstream target genes to control diverse processes. Here, we discuss the signals to and from DAF-16, with a focus on life span regulation.
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Biogerontology,
2015]
In C. elegans, mutations in the conserved insulin/IGF-1 signaling (IIS) pathway lead to a robust extension in lifespan, improved late life health, and protection from age-related disease. These effects are mediated by the FoxO transcription factor DAF-16 which lies downstream of the IIS kinase cascade. Identifying and functionally testing DAF-16 target genes has been a focal point of ageing research for the last 10years. Here, I review the recent advances in identifying and understanding IIS/DAF-16 targets. These studies continue to reveal the intricate nature of the IIS/DAF-16 gene regulation network and are helping us to understand the mechanisms that control lifespan. Ageing and age related disease is an area of intense public interest, and the biochemical characterization of the genes involved will be critical for identifying drugs to improve the health of our ageing population.
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Semin Nephrol,
2006]
The vacuolar H(+)-ATPase is a multisubunit protein consisting of a peripheral catalytic domain (V(1)) that binds and hydrolyzes adenosine triphosphate (ATP) and provides energy to pump H(+) through the transmembrane domain (V(0)) against a large gradient. This proton-translocating vacuolar H(+)-ATPase is present in both intracellular compartments and the plasma membrane of eukaryotic cells. Mutations in genes encoding kidney intercalated cell-specific V(0)
a4 and V(1) B1 subunits of the vacuolar H(+)-ATPase cause the syndrome of distal tubular renal acidosis. This review focuses on the function, regulation, and the role of vacuolar H(+)-ATPases in renal physiology. The localization of vacuolar H(+)-ATPases in the kidney, and their role in intracellular pH (pHi) regulation, transepithelial proton transport, and acid-base homeostasis are discussed.
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Ann N Y Acad Sci,
2010]
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.
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Front Pharmacol,
2017]
Aging is associated with age-related diseases and an increase susceptibility of cancer. Dissecting the molecular mechanisms that underlie aging and longevity would contribute to implications for preventing and treating the age-dependent diseases or cancers. Multiple signaling pathways such as the insulin/IGF-1 signaling pathway, TOR signaling, AMPK pathway, JNK pathway and germline signaling have been found to be involved in aging and longevity. And DAF-16/FOXO, as a key transcription factor, could integrate different signals from these pathways to modulate aging, and longevity via shuttling from cytoplasm to nucleus. Hence, understanding how DAF-16/FOXO functions will be pivotal to illustrate the processes of aging and longevity. Here, we summarized how DAF-16/FOXO receives signals from these pathways to affect aging and longevity. We also briefly discussed the transcriptional regulation and posttranslational modifications of DAF-16/FOXO, its co-factors as well as its potential downstream targets participating in lifespan according to the published data in C. elegans and in mammals, and in most cases, we may focus on the studies in C. elegans which has been considered to be a very good animal model for longevity research.
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Exp Gerontol,
2006]
The insulin/IGF-1 receptor (IIR)/FOXO pathway is remarkably conserved in worms, flies, and mammals, and downregulation of signaling in this pathway has been shown to extend lifespan in all of these animals. FOXO-mediated transcription is required for the long lifespan of IIR mutants; thus, there is great interest in identifying FOXO target genes, as they may carry out the biochemical activities that extend longevity. A number of approaches have been used to identify the transcriptional targets of FOXO. Thus far, the best data available on the components downstream of this pathway are from experiments involving the Caenorhabditis elegans FOXO transcription factor, DAF-16; some of these targets have been tested for their contributions to longevity, dauer formation, and fat storage. Here, I examine and compare the approaches used to identify DAF-16/FOXO targets, review the genes regulated by DAF-16, and discuss the processes that may be at work to extend lifespan in IIR mutants. Rather than upregulating every possible beneficial gene, DAF-16 appears to selectively upregulate genes that contribute to specific protective mechanisms, while simultaneously downregulating potentially deleterious genes. In addition to genes that carry out expected roles in stress protection, many previously unknown targets have been identified in these studies, suggesting that some mechanisms of lifespan extension still await discovery. These mechanisms may act cooperatively or cumulatively to increase longevity, and are likely to be at least partially conserved in higher organisms.