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Abstract
Over the past decade, studies conducted in Caenorhabditis elegans have helped to uncover the ancient and complex origins of body fat regulation. This review highlights the powerful combination of genetics, pharmacology, and biochemistry used to study energy balance and the regulation of cellular fat metabolism in C. elegans. The complete wiring diagram of the C. elegans nervous system has been exploited to understand how the sensory nervous system regulates body fat and how food perception is coupled with the production of energy via fat metabolism. As a model organism, C. elegans also offers a unique opportunity to discover neuroendocrine factors that mediate direct communication between the nervous system and the metabolic tissues. The coming years are expected to reveal a wealth of information on the neuroendocrine control of body fat in C. elegans.
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Affiliation(s)
- Supriya Srinivasan
- Department of Chemical Physiology and Dorris Neuroscience Center, The Scripps Research Institute (TSRI), La Jolla, California 92037;
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102
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Genome-wide evaluation of the interplay between Caenorhabditis elegans and Yersinia pseudotuberculosis during in vivo biofilm formation. Infect Immun 2014; 83:17-27. [PMID: 25312958 DOI: 10.1128/iai.00110-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The formation of an incapacitating biofilm on Caenorhabditis elegans by Yersinia pseudotuberculosis represents a tractable model for investigating the genetic basis for host-pathogen interplay during the biofilm-mediated infection of a living surface. Previously we established a role for quorum sensing (QS) and the master motility regulator, FlhDC, in biofilm formation by Y. pseudotuberculosis on C. elegans. To obtain further genome-wide insights, we used transcriptomic analysis to obtain comparative information on C. elegans in the presence and absence of biofilm and on wild-type Y. pseudotuberculosis and Y. pseudotuberculosis QS mutants. Infection of C. elegans with the wild-type Y. pseudotuberculosis resulted in the differential regulation of numerous genes, including a distinct subset of nematode C-lectin (clec) and fatty acid desaturase (fat) genes. Evaluation of the corresponding C. elegans clec-49 and fat-3 deletion mutants showed delayed biofilm formation and abolished biofilm formation, respectively. Transcriptomic analysis of Y. pseudotuberculosis revealed that genes located in both of the histidine utilization (hut) operons were upregulated in both QS and flhDC mutants. In addition, mutation of the regulatory gene hutC resulted in the loss of biofilm, increased expression of flhDC, and enhanced swimming motility. These data are consistent with the existence of a regulatory cascade in which the Hut pathway links QS and flhDC. This work also indicates that biofilm formation by Y. pseudotuberculosis on C. elegans is an interactive process during which the initial attachment/recognition of Yersinia to/by C. elegans is followed by bacterial growth and biofilm formation.
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103
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SKN-1 and Nrf2 couples proline catabolism with lipid metabolism during nutrient deprivation. Nat Commun 2014; 5:5048. [PMID: 25284427 PMCID: PMC4205844 DOI: 10.1038/ncomms6048] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 08/20/2014] [Indexed: 02/01/2023] Open
Abstract
Mechanisms that coordinate different metabolic pathways, such as glucose and lipid, have been recognized. However, a potential interaction between amino acid and lipid metabolism remains largely elusive. Here we show that during starvation of Caenorhabditis elegans, proline catabolism is coupled with lipid metabolism by SKN-1. Mutation of alh-6, a conserved proline catabolic enzyme, accelerates fat mobilization, enhances the expression of genes involved in fatty acid oxidation and reduces survival in response to fasting. This metabolic coordination is mediated by the activation of the transcription factor SKN-1/Nrf2, possibly due to the accumulation of the alh-6 substrate P5C, and also requires the transcriptional co-regulator MDT-15. Constitutive activation of SKN-1 induces a similar transcriptional response, which protects animals from fat accumulation when fed a high carbohydrate diet. In human cells, an orthologous alh-6 enzyme, ALDH4A1, is also linked to the activity of Nrf2, the human orthologue of SKN-1, and regulates the expression of lipid metabolic genes. Our findings identify a link between proline catabolism and lipid metabolism, and uncover a physiological role for SKN-1 in metabolism. The coordinated metabolism of cellular nutrients is important to maintain energy homeostasis, particularly if nutrients are scarce. Here, the authors report that the sensor protein SKN-1/Nrf2 links catabolism of the amino acid proline with lipid metabolism in C. elegans and in cultured human cells.
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104
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PKG and NHR-49 signalling co-ordinately regulate short-term fasting-induced lysosomal lipid accumulation in C. elegans. Biochem J 2014; 461:509-20. [PMID: 24854345 DOI: 10.1042/bj20140191] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Lysosomes act as terminal degradation organelles to hydrolyse macromolecules derived from both the extracellular space and the cytoplasm. In Caenorhabditis elegans fasting induces the lysosomal compartment to expand. However, the molecular and cellular mechanisms for this stress response remain largely unclear. In the present study, we find that short-term fasting leads to increased accumulation of polar lipids in lysosomes. The fasting response is co-ordinately regulated by EGL-4, the C. elegans PKG (protein kinase G) orthologue, and nuclear hormone receptor NHR-49. Further results demonstrate that EGL-4 acts in sensory neurons to enhance lysosomal lipid accumulation through inhibiting the DAF-3/SMAD pathway, whereas NHR-49 acts in intestine to inhibit lipids accumulation via activation of IPLA-2 (intracellular membrane-associated calcium-independent phospholipase A2) in cytoplasm and other hydrolases in lysosomes. Remarkably, the lysosomal lipid accumulation is independent of autophagy and RAB-7-mediated endocytosis. Taken together, our results reveal a new mechanism for lysosomal lipid metabolism during the stress response, which may provide new clues for investigations of lysosome function in energy homoeostasis.
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105
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Lemieux GA, Ashrafi K. Insights and challenges in using C. elegans for investigation of fat metabolism. Crit Rev Biochem Mol Biol 2014; 50:69-84. [PMID: 25228063 DOI: 10.3109/10409238.2014.959890] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
C. elegans provides a genetically tractable system for deciphering the homeostatic mechanisms that underlie fat regulation in intact organisms. Here, we provide an overview of the recent advances in the C. elegans fat field with particular attention to studies of C. elegans lipid droplets, the complex links between lipases, autophagy, and lifespan, and analyses of key transcriptional regulatory mechanisms that coordinate lipid homeostasis. These studies demonstrate the ancient origins of mammalian and C. elegans fat regulatory pathways and highlight how C. elegans is being used to identify and analyze novel lipid pathways that are then shown to function similarly in mammals. Despite its many advantages, study of fat regulation in C. elegans is currently faced with a number of conceptual and methodological challenges. We critically evaluate some of the assumptions in the field and highlight issues that we believe should be taken into consideration when interpreting lipid content data in C. elegans.
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Affiliation(s)
- George A Lemieux
- Department of Physiology, University of California , San Francisco, CA , USA
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106
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Lipid droplet protein LID-1 mediates ATGL-1-dependent lipolysis during fasting in Caenorhabditis elegans. Mol Cell Biol 2014; 34:4165-76. [PMID: 25202121 DOI: 10.1128/mcb.00722-14] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipolysis is a delicate process involving complex signaling cascades and sequential enzymatic activations. In Caenorhabditis elegans, fasting induces various physiological changes, including a dramatic decrease in lipid contents through lipolysis. Interestingly, C. elegans lacks perilipin family genes which play a crucial role in the regulation of lipid homeostasis in other species. Here, we demonstrate that in the intestinal cells of C. elegans, a newly identified protein, lipid droplet protein 1 (C25A1.12; LID-1), modulates lipolysis by binding to adipose triglyceride lipase 1 (C05D11.7; ATGL-1) during nutritional deprivation. In fasted worms, lipid droplets were decreased in intestinal cells, whereas suppression of ATGL-1 via RNA interference (RNAi) resulted in retention of stored lipid droplets. Overexpression of ATGL-1 markedly decreased lipid droplets, whereas depletion of LID-1 via RNAi prevented the effect of overexpressed ATGL-1 on lipolysis. In adult worms, short-term fasting increased cyclic AMP (cAMP) levels, which activated protein kinase A (PKA) to stimulate lipolysis via ATGL-1 and LID-1. Moreover, ATGL-1 protein stability and LID-1 binding were augmented by PKA activation, eventually leading to increased lipolysis. These data suggest the importance of the concerted action of lipase and lipid droplet protein in the response to fasting signals via PKA to maintain lipid homeostasis.
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107
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Nuclear receptors in nematode development: Natural experiments made by a phylum. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:224-37. [PMID: 24984201 DOI: 10.1016/j.bbagrm.2014.06.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 06/21/2014] [Accepted: 06/23/2014] [Indexed: 11/21/2022]
Abstract
The development of complex multicellular organisms is dependent on regulatory decisions that are necessary for the establishment of specific differentiation and metabolic cellular states. Nuclear receptors (NRs) form a large family of transcription factors that play critical roles in the regulation of development and metabolism of Metazoa. Based on their DNA binding and ligand binding domains, NRs are divided into eight NR subfamilies from which representatives of six subfamilies are present in both deuterostomes and protostomes indicating their early evolutionary origin. In some nematode species, especially in Caenorhabditis, the family of NRs expanded to a large number of genes strikingly exceeding the number of NR genes in vertebrates or insects. Nematode NRs, including the multiplied Caenorhabditis genes, show clear relation to vertebrate and insect homologues belonging to six of the eight main NR subfamilies. This review summarizes advances in research of nematode NRs and their developmental functions. Nematode NRs can reveal evolutionarily conserved mechanisms that regulate specific developmental and metabolic processes as well as new regulatory adaptations. They represent the results of a large number of natural experiments with structural and functional potential of NRs for the evolution of the phylum. The conserved and divergent character of nematode NRs adds a new dimension to our understanding of the general biology of regulation by NRs. This article is part of a Special Issue entitled: Nuclear receptors in animal development.
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108
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Khan MH, Ligon M, Hussey LR, Hufnal B, Farber R, Munkácsy E, Rodriguez A, Dillow A, Kahlig E, Rea SL. TAF-4 is required for the life extension of isp-1, clk-1 and tpk-1 Mit mutants. Aging (Albany NY) 2014; 5:741-58. [PMID: 24107417 PMCID: PMC3838777 DOI: 10.18632/aging.100604] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
While numerous life-extending manipulations have been discovered in the nematode Caenorhabditis elegans, one that remains most enigmatic is disruption of oxidative phosphorylation. In order to unravel how such an ostensibly deleterious manipulation can extend lifespan, we sought to identify the ensemble of nuclear transcription factors that are activated in response to defective mitochondrial electron transport chain (ETC) function. Using a feeding RNAi approach, we targeted over 400 transcription factors and identified 15 that, when reduced in function, reproducibly and differentially altered the development, stress response, and/or fecundity of isp-1(qm150) Mit mutants relative to wild-type animals. Seven of these transcription factors – AHA-1, CEH-18, HIF-1, JUN-1, NHR-27, NHR-49 and the CREB homolog-1 (CRH-1)-interacting protein TAF-4 – were also essential for isp-1 life extension. When we tested the involvement of these seven transcription factors in the life extension of two other Mit mutants, namely clk-1(qm30) and tpk-1(qm162), TAF-4 and HIF-1 were consistently required. Our findings suggest that the Mit phenotype is under the control of multiple transcriptional responses, and that TAF-4 and HIF-1 may be part of a general signaling axis that specifies Mit mutant life extension.
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Affiliation(s)
- Maruf H Khan
- Barshop Institute for Longevity and Aging Studies and Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78245, USA
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109
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Guo X, García LR. SIR-2.1 integrates metabolic homeostasis with the reproductive neuromuscular excitability in early aging male Caenorhabditis elegans. eLife 2014; 3:e01730. [PMID: 24755287 PMCID: PMC3989601 DOI: 10.7554/elife.01730] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 03/16/2014] [Indexed: 01/29/2023] Open
Abstract
The decline of aging C. elegans male's mating behavior is correlated with the increased excitability of the cholinergic circuitry that executes copulation. In this study, we show that the mating circuits' functional durability depends on the metabolic regulator SIR-2.1, a NAD(+)-dependent histone deacetylase. Aging sir-2.1(0) males display accelerated mating behavior decline due to premature hyperexcitability of cholinergic circuits used for intromission and ejaculation. In sir-2.1(0) males, the hypercontraction of the spicule-associated muscles pinch the vas deferens opening, thus blocking sperm release. The hyperexcitability is aggravated by reactive oxygen species (ROS). Our genetic, pharmacological, and behavioral analyses suggest that in sir-2.1(0) and older wild-type males, enhanced catabolic enzymes expression, coupled with the reduced expression of ROS-scavengers contribute to the behavioral decline. However, as a compensatory response to reduce altered catabolism/ROS production, anabolic enzymes expression levels are also increased, resulting in higher gluconeogenesis and lipid synthesis. DOI: http://dx.doi.org/10.7554/eLife.01730.001.
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Affiliation(s)
- Xiaoyan Guo
- Department of Biology, Texas A&M University, College Station, United States
| | - L René García
- Department of Biology, Texas A&M University, College Station, United States
- Howard Hughes Medical Institute, Texas A&M University, Texas, United States
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110
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Ehmke M, Luthe K, Schnabel R, Döring F. S-Adenosyl methionine synthetase 1 limits fat storage in Caenorhabditis elegans. GENES & NUTRITION 2014; 9:386. [PMID: 24510589 PMCID: PMC3968293 DOI: 10.1007/s12263-014-0386-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 01/27/2014] [Indexed: 11/30/2022]
Abstract
Cytosolic lipid droplets are versatile, evolutionarily conserved organelles that are important for the storage and utilization of lipids in almost all cell types. To obtain insight into the physiological importance of lipid droplet size, we isolated and characterized a new S-adenosyl methionine synthetase 1 (SAMS-1)-deficient Caenorhabditis elegans mutant, which have enlarged lipid droplets throughout its life cycle. We found that the sams-1 mutant showed a markedly reduced body size and progeny number; impaired synthesis of phosphatidylcholine, a major membrane phospholipid; and elevated expression of key lipogenic genes, such as dgat-2, resulting in the accumulation of triacylglyceride in fewer, but larger, lipid droplets. The sams-1 mutant store more than 50 % (wild type: 10 %) of its intestinal fat in large lipid droplets, ≥10 μm(3) in size. In response to starvation, SAMS-1 deficiency causes reduced depletion of a subset of lipid droplets located in the anterior intestine. Given the importance of liberation of fatty acids from lipid droplets, we propose that the physiological function of SAMS-1, a highly conserved enzyme involved in one-carbon metabolism, is the limitation of fat storage to ensure proper growth and reproduction.
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Affiliation(s)
- Madeleine Ehmke
- />Department of Molecular Prevention, Institute of Human Nutrition and Food Sciences, University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany
| | - Katharina Luthe
- />Department of Developmental Genetics, Institute of Genetics, TU Braunschweig, Spielmannstr. 7, 38106 Brunswick, Germany
| | - Ralf Schnabel
- />Department of Developmental Genetics, Institute of Genetics, TU Braunschweig, Spielmannstr. 7, 38106 Brunswick, Germany
| | - Frank Döring
- />Department of Molecular Prevention, Institute of Human Nutrition and Food Sciences, University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany
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111
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Elle IC, Rødkær SV, Fredens J, Færgeman NJ. A method for measuring fatty acid oxidation in C. elegans. WORM 2013; 1:26-30. [PMID: 24058820 PMCID: PMC3670168 DOI: 10.4161/worm.19564] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
The nematode C. elegans has during the past decade proven to be a valuable model organism to identify and examine molecular mechanisms regulating lipid storage and metabolism. While the primary approach has been to identify genes and pathways conferring alterations in lipid accumulation, only a few recent studies have recognized the central role of fatty acid degradation in cellular lipid homeostasis. In the present study, we show how complete oxidation of fatty acids can be determined in live C. elegans by examining oxidation of tritium-labeled fatty acids to tritiated H2O that can be measured by scintillation counting. Treating animals with sodium azide, an inhibitor of the electron transport chain, reduced 3H2O production to approximately 15%, while boiling of animals prior to assay completely blocked the production of labeled water. We demonstrate that worms fed different bacterial strains exhibit different fatty acid oxidation rates. We show that starvation results in increased fatty acid oxidation, which is independent of the transcription factor NHR-49. On the contrary, fatty acid oxidation is reduced to approximately 70% in animals lacking the worm homolog of the insulin receptor, DAF-2. Hence, the present methodology can be used to delineate the role of specific genes and pathways in the regulation of β-oxidation in C. elegans.
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Affiliation(s)
- Ida Coordt Elle
- Department of Biochemistry and Molecular Biology; University of Southern Denmark; Odense, Denmark
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112
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Magner DB, Wollam J, Shen Y, Hoppe C, Li D, Latza C, Rottiers V, Hutter H, Antebi A. The NHR-8 nuclear receptor regulates cholesterol and bile acid homeostasis in C. elegans. Cell Metab 2013; 18:212-24. [PMID: 23931753 PMCID: PMC3909615 DOI: 10.1016/j.cmet.2013.07.007] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 05/17/2013] [Accepted: 07/15/2013] [Indexed: 12/17/2022]
Abstract
Hormone-gated nuclear receptors (NRs) are conserved transcriptional regulators of metabolism, reproduction, and homeostasis. Here we show that C. elegans NHR-8 NR, a homolog of vertebrate liver X and vitamin D receptors, regulates nematode cholesterol balance, fatty acid desaturation, apolipoprotein production, and bile acid metabolism. Loss of nhr-8 results in a deficiency in bile acid-like steroids, called the dafachronic acids, which regulate the related DAF-12/NR, thus controlling entry into the long-lived dauer stage through cholesterol availability. Cholesterol supplementation rescues various nhr-8 phenotypes, including developmental arrest, unsaturated fatty acid deficiency, reduced fertility, and shortened life span. Notably, nhr-8 also interacts with daf-16/FOXO to regulate steady-state cholesterol levels and is synthetically lethal in combination with insulin signaling mutants that promote unregulated growth. Our studies provide important insights into nuclear receptor control of cholesterol balance and metabolism and their impact on development, reproduction, and aging in the context of larger endocrine networks.
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Affiliation(s)
- Daniel B Magner
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse, Cologne, Germany
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113
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Baugh LR. To grow or not to grow: nutritional control of development during Caenorhabditis elegans L1 arrest. Genetics 2013; 194:539-55. [PMID: 23824969 PMCID: PMC3697962 DOI: 10.1534/genetics.113.150847] [Citation(s) in RCA: 176] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 05/09/2013] [Indexed: 12/30/2022] Open
Abstract
It is widely appreciated that larvae of the nematode Caenorhabditis elegans arrest development by forming dauer larvae in response to multiple unfavorable environmental conditions. C. elegans larvae can also reversibly arrest development earlier, during the first larval stage (L1), in response to starvation. "L1 arrest" (also known as "L1 diapause") occurs without morphological modification but is accompanied by increased stress resistance. Caloric restriction and periodic fasting can extend adult lifespan, and developmental models are critical to understanding how the animal is buffered from fluctuations in nutrient availability, impacting lifespan. L1 arrest provides an opportunity to study nutritional control of development. Given its relevance to aging, diabetes, obesity and cancer, interest in L1 arrest is increasing, and signaling pathways and gene regulatory mechanisms controlling arrest and recovery have been characterized. Insulin-like signaling is a critical regulator, and it is modified by and acts through microRNAs. DAF-18/PTEN, AMP-activated kinase and fatty acid biosynthesis are also involved. The nervous system, epidermis, and intestine contribute systemically to regulation of arrest, but cell-autonomous signaling likely contributes to regulation in the germline. A relatively small number of genes affecting starvation survival during L1 arrest are known, and many of them also affect adult lifespan, reflecting a common genetic basis ripe for exploration. mRNA expression is well characterized during arrest, recovery, and normal L1 development, providing a metazoan model for nutritional control of gene expression. In particular, post-recruitment regulation of RNA polymerase II is under nutritional control, potentially contributing to a rapid and coordinated response to feeding. The phenomenology of L1 arrest will be reviewed, as well as regulation of developmental arrest and starvation survival by various signaling pathways and gene regulatory mechanisms.
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Affiliation(s)
- L Ryan Baugh
- Department of Biology, Duke Center for Systems Biology, Duke University, Durham, North Carolina 27708-0338, USA.
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114
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MXL-3 and HLH-30 transcriptionally link lipolysis and autophagy to nutrient availability. Nat Cell Biol 2013; 15:668-76. [PMID: 23604316 DOI: 10.1038/ncb2741] [Citation(s) in RCA: 231] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Accepted: 03/22/2013] [Indexed: 11/08/2022]
Abstract
Fat is stored or mobilized according to food availability. Malfunction of the mechanisms that ensure this coordination underlie metabolic diseases in humans. In mammals, lysosomal and autophagic function is required for normal fat storage and mobilization in the presence or absence of food. Autophagy is tightly linked to nutrients. However, if and how lysosomal lipolysis is coupled to nutritional status remains to be determined. Here we identify MXL-3 and HLH-30 (TFEB orthologue) [corrected] as transcriptional switches coupling lysosomal lipolysis and autophagy to nutrient availability and controlling fat storage and ageing in Caenorhabditis elegans. Transcriptional coupling of lysosomal lipolysis and autophagy to nutrients is also observed in mammals. Thus, MXL-3 and HLH-30 orchestrate an adaptive and conserved cellular response to nutritional status and regulate lifespan.
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115
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TFEB controls cellular lipid metabolism through a starvation-induced autoregulatory loop. Nat Cell Biol 2013; 15:647-58. [PMID: 23604321 DOI: 10.1038/ncb2718] [Citation(s) in RCA: 722] [Impact Index Per Article: 65.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 10/26/2013] [Indexed: 12/27/2022]
Abstract
The lysosomal-autophagic pathway is activated by starvation and plays an important role in both cellular clearance and lipid catabolism. However, the transcriptional regulation of this pathway in response to metabolic cues is uncharacterized. Here we show that the transcription factor EB (TFEB), a master regulator of lysosomal biogenesis and autophagy, is induced by starvation through an autoregulatory feedback loop and exerts a global transcriptional control on lipid catabolism via Ppargc1α and Ppar1α. Thus, during starvation a transcriptional mechanism links the autophagic pathway to cellular energy metabolism. The conservation of this mechanism in Caenorhabditis elegans suggests a fundamental role for TFEB in the evolution of the adaptive response to food deprivation. Viral delivery of TFEB to the liver prevented weight gain and metabolic syndrome in both diet-induced and genetic mouse models of obesity, suggesting a new therapeutic strategy for disorders of lipid metabolism.
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116
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Yu Z, Zhang J, Chen X, Yin D, Deng H. Inhibitions on the behavior and growth of the nematode progeny after prenatal exposure to sulfonamides at micromolar concentrations. JOURNAL OF HAZARDOUS MATERIALS 2013; 250-251:198-203. [PMID: 23454458 DOI: 10.1016/j.jhazmat.2013.01.078] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 01/27/2013] [Accepted: 01/31/2013] [Indexed: 06/01/2023]
Abstract
Sulfonamides are one typical antibiotic which is an emerging hazardous material to the ecological stability due to their continuously application and biological effects to non-target organisms. The parent-progeny transgenerational effects need investigations to indicate their long-term consequences. Currently, we tested the transgenerational effects of sulfadiazine (SD), sulfapyridine (SP) and sulfamethazine (SMZ) on L3 larva of Caenorhabditis elegans. The nematodes were exposed to aqueous sulfonamides at micromolar concentrations for 96 h, and then the effects on the behavior and growth in the exposed parent and unexposed progeny were measured. Results showed that SD, SP and SMZ inhibited three behavior indicators including body bending frequency (BBF), reversal movement (RM) and Omega turn (OT), and the growth indicator (body length, BL). Behavior indicators showed higher sensitivities than the growth indicator, and BBF had the highest sensitivity among the behavior indicators. Moreover, the effects of sulfonamides were also observed in the unexposed progeny with partially rescued or more severe inhibitions on the indicators. The behavior also showed higher sensitivity than the growth in the progeny. The transgenerational effects of sulfonamides indicated that parental exposure can multiply the harmful effects of antibiotic pollution in following generations and their potential ecological risks at environmental concentrations were further raised.
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Affiliation(s)
- ZhenYang Yu
- Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
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117
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MacNeil L, Watson E, Arda HE, Zhu LJ, Walhout AJ. Diet-induced developmental acceleration independent of TOR and insulin in C. elegans. Cell 2013; 153:240-52. [PMID: 23540701 PMCID: PMC3821073 DOI: 10.1016/j.cell.2013.02.049] [Citation(s) in RCA: 185] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Revised: 12/18/2012] [Accepted: 02/05/2013] [Indexed: 12/16/2022]
Abstract
Dietary composition has major effects on physiology. Here, we show that developmental rate, reproduction, and lifespan are altered in C. elegans fed Comamonas DA1877 relative to those fed a standard E. coli OP50 diet. We identify a set of genes that change in expression in response to this diet and use the promoter of one of these (acdh-1) as a dietary sensor. Remarkably, the effects on transcription and development occur even when Comamonas DA1877 is diluted with another diet, suggesting that Comamonas DA1877 generates a signal that is sensed by the nematode. Surprisingly, the developmental effect is independent from TOR and insulin signaling. Rather, Comamonas DA1877 affects cyclic gene expression during molting, likely through the nuclear hormone receptor NHR-23. Altogether, our findings indicate that different bacteria elicit various responses via distinct mechanisms, which has implications for diseases such as obesity and the interactions between the human microbiome and intestinal cells.
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Affiliation(s)
| | - Emma Watson
- Program in Systems Biology
- Program in Molecular Medicine
| | - H. Efsun Arda
- Program in Systems Biology
- Program in Molecular Medicine
| | - Lihua Julie Zhu
- Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA, University of Massachusetts Medical School, Worcester, MA
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118
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Watson E, MacNeil LT, Arda HE, Zhu LJ, Walhout AJ. Integration of metabolic and gene regulatory networks modulates the C. elegans dietary response. Cell 2013; 153:253-66. [PMID: 23540702 PMCID: PMC3817025 DOI: 10.1016/j.cell.2013.02.050] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 12/15/2012] [Accepted: 02/05/2013] [Indexed: 12/16/2022]
Abstract
Expression profiles are tailored according to dietary input. However, the networks that control dietary responses remain largely uncharacterized. Here, we combine forward and reverse genetic screens to delineate a network of 184 genes that affect the C. elegans dietary response to Comamonas DA1877 bacteria. We find that perturbation of a mitochondrial network composed of enzymes involved in amino acid metabolism and the TCA cycle affects the dietary response. In humans, mutations in the corresponding genes cause inborn diseases of amino acid metabolism, most of which are treated by dietary intervention. We identify several transcription factors (TFs) that mediate the changes in gene expression upon metabolic network perturbations. Altogether, our findings unveil a transcriptional response system that is poised to sense dietary cues and metabolic imbalances, illustrating extensive communication between metabolic networks in the mitochondria and gene regulatory networks in the nucleus.
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Affiliation(s)
- Emma Watson
- Program in Systems Biology, University of Massachusetts Medical School, Worcester, MA
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Lesley T. MacNeil
- Program in Systems Biology, University of Massachusetts Medical School, Worcester, MA
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA
| | - H. Efsun Arda
- Program in Systems Biology, University of Massachusetts Medical School, Worcester, MA
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Lihua Julie Zhu
- Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA
| | - Albertha J.M. Walhout
- Program in Systems Biology, University of Massachusetts Medical School, Worcester, MA
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA
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119
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Zhang Y, Zou X, Ding Y, Wang H, Wu X, Liang B. Comparative genomics and functional study of lipid metabolic genes in Caenorhabditis elegans. BMC Genomics 2013; 14:164. [PMID: 23496871 PMCID: PMC3602672 DOI: 10.1186/1471-2164-14-164] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 03/06/2013] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Animal models are indispensable to understand the lipid metabolism and lipid metabolic diseases. Over the last decade, the nematode Caenorhabditis elegans has become a popular animal model for exploring the regulation of lipid metabolism, obesity, and obese-related diseases. However, the genomic and functional conservation of lipid metabolism from C. elegans to humans remains unknown. In the present study, we systematically analyzed genes involved in lipid metabolism in the C. elegans genome using comparative genomics. RESULTS We built a database containing 471 lipid genes from the C. elegans genome, and then assigned most of lipid genes into 16 different lipid metabolic pathways that were integrated into a network. Over 70% of C. elegans lipid genes have human orthologs, with 237 of 471 C. elegans lipid genes being conserved in humans, mice, rats, and Drosophila, of which 71 genes are specifically related to human metabolic diseases. Moreover, RNA-mediated interference (RNAi) was used to disrupt the expression of 356 of 471 lipid genes with available RNAi clones. We found that 21 genes strongly affect fat storage, development, reproduction, and other visible phenotypes, 6 of which have not previously been implicated in the regulation of fat metabolism and other phenotypes. CONCLUSIONS This study provides the first systematic genomic insight into lipid metabolism in C. elegans, supporting the use of C. elegans as an increasingly prominent model in the study of metabolic diseases.
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Affiliation(s)
- Yuru Zhang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
| | - Xiaoju Zou
- Department of Life Science and Biotechnology, Kunming University, Kunming 650214, China
| | - Yihong Ding
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
| | - Haizhen Wang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
| | - Xiaoyun Wu
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
| | - Bin Liang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Kunming Institute of Zoology, Chinese Academy of Sciences, 32 Jiao-Chang Dong Road, Kunming, Yunnan 650223, China
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120
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O'Rourke EJ, Kuballa P, Xavier R, Ruvkun G. ω-6 Polyunsaturated fatty acids extend life span through the activation of autophagy. Genes Dev 2013; 27:429-40. [PMID: 23392608 DOI: 10.1101/gad.205294.112] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Adaptation to nutrient scarcity depends on the activation of metabolic programs to efficiently use internal reserves of energy. Activation of these programs in abundant food regimens can extend life span. However, the common molecular and metabolic changes that promote adaptation to nutritional stress and extend life span are mostly unknown. Here we present a response to fasting, enrichment of ω-6 polyunsaturated fatty acids (PUFAs), which promotes starvation resistance and extends Caenorhabditis elegans life span. Upon fasting, C. elegans induces the expression of a lipase, which in turn leads to an enrichment of ω-6 PUFAs. Supplementing C. elegans culture media with these ω-6 PUFAs increases their resistance to starvation and extends their life span in conditions of food abundance. Supplementation of C. elegans or human epithelial cells with these ω-6 PUFAs activates autophagy, a cell recycling mechanism that promotes starvation survival and slows aging. Inactivation of C. elegans autophagy components reverses the increase in life span conferred by supplementing the C. elegans diet with these fasting-enriched ω-6 PUFAs. We propose that the salubrious effects of dietary supplementation with ω-3/6 PUFAs (fish oils) that have emerged from epidemiological studies in humans may be due to a similar activation of autophagic programs.
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Affiliation(s)
- Eyleen J O'Rourke
- Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
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121
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Grompone G, Martorell P, Llopis S, González N, Genovés S, Mulet AP, Fernández-Calero T, Tiscornia I, Bollati-Fogolín M, Chambaud I, Foligné B, Montserrat A, Ramón D. Anti-inflammatory Lactobacillus rhamnosus CNCM I-3690 strain protects against oxidative stress and increases lifespan in Caenorhabditis elegans. PLoS One 2012; 7:e52493. [PMID: 23300685 PMCID: PMC3530454 DOI: 10.1371/journal.pone.0052493] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 11/19/2012] [Indexed: 01/15/2023] Open
Abstract
Numerous studies have shown that resistance to oxidative stress is crucial to stay healthy and to reduce the adverse effects of aging. Accordingly, nutritional interventions using antioxidant food-grade compounds or food products are currently an interesting option to help improve health and quality of life in the elderly. Live lactic acid bacteria (LAB) administered in food, such as probiotics, may be good antioxidant candidates. Nevertheless, information about LAB-induced oxidative stress protection is scarce. To identify and characterize new potential antioxidant probiotic strains, we have developed a new functional screening method using the nematode Caenorhabditis elegans as host. C. elegans were fed on different LAB strains (78 in total) and nematode viability was assessed after oxidative stress (3 mM and 5 mM H(2)O(2)). One strain, identified as Lactobacillus rhamnosus CNCM I-3690, protected worms by increasing their viability by 30% and, also, increased average worm lifespan by 20%. Moreover, transcriptomic analysis of C. elegans fed with this strain showed that increased lifespan is correlated with differential expression of the DAF-16/insulin-like pathway, which is highly conserved in humans. This strain also had a clear anti-inflammatory profile when co-cultured with HT-29 cells, stimulated by pro-inflammatory cytokines, and co-culture systems with HT-29 cells and DC in the presence of LPS. Finally, this Lactobacillus strain reduced inflammation in a murine model of colitis. This work suggests that C. elegans is a fast, predictive and convenient screening tool to identify new potential antioxidant probiotic strains for subsequent use in humans.
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122
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Webster CM, Deline ML, Watts JL. Stress response pathways protect germ cells from omega-6 polyunsaturated fatty acid-mediated toxicity in Caenorhabditis elegans. Dev Biol 2012; 373:14-25. [PMID: 23064027 DOI: 10.1016/j.ydbio.2012.10.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2012] [Revised: 09/24/2012] [Accepted: 10/01/2012] [Indexed: 12/31/2022]
Abstract
Polyunsaturated fatty acids serve both structural and functional roles as membrane components and precursors for a number of different factors involved in inflammation and signaling. These fatty acids are required in the human diet, although excess dietary intake of omega-6 fatty polyunsaturated fatty acids may have a negative influence on human health. In the model nematode, Caenorhabditis elegans, dietary exposure to dihomo-gamma-linolenic acid (DGLA), an omega-6 fatty acid, causes the destruction of germ cells and leads to sterility. In this study we used genetic and microscopic approaches to further characterize this phenomenon. We found that strains carrying mutations in genes involved in lipid homeostasis enhanced sterility phenotypes, while mutations reducing the activity of the conserved insulin/IGF signaling pathway suppressed sterility phenotypes. Exposure to a mild heat stress prior to omega-6 fatty acid treatment led to an adaptive or hormetic response, resulting in less sterility. Mutations in skn-1 and knockdown of genes encoding phase II detoxification enzymes led to increased sterility in the presence of dietary DGLA. Thus, detoxification systems and genetic changes that increase overall stress responses protect the germ cells from destruction. Microscopic analyses revealed that dietary DGLA leads to deterioration of germ cell membranes in the proliferative and transition zones of the developing germ line. Together, these data demonstrate that specific omega-6 polyunsaturated fatty acids, or molecules derived from them, are transported to the germ line where they disrupt the rapidly expanding germ cell membranes, leading to germ cell death.
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Affiliation(s)
- Christopher M Webster
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA 99614-6340, USA
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123
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McGhee JD. TheCaenorhabditis elegansintestine. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 2:347-67. [DOI: 10.1002/wdev.93] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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124
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Kim SH, Bae YA, Nam JS, Yang Y, Nawa Y, Kong Y. Fatty acid compositions of Taenia solium metacestode and its surrounding tissues. Parasitol Int 2012; 62:75-8. [PMID: 22971473 DOI: 10.1016/j.parint.2012.08.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Revised: 08/08/2012] [Accepted: 08/10/2012] [Indexed: 11/25/2022]
Abstract
Fatty acids (FAs) are the main energy sources of living organisms and are the major components of cellular and organelle membranes. Their compositions also affect the flexibility/rigidity of cells and cell vitality. The Taenia solium metacestode (TsM) causes neurocysticercosis (NC), which is one of the most common helminthic infections of the central nerve system. We investigated the FA composition of the cyst fluid (CF) and parenchyma of the TsM, together with those of the granuloma and swine tissue surrounding the granuloma. The FA fractions of the TsM CF and swine tissue showed a composition and proportional contents comparable to each other, in which C18:0 (stearic acid), C18:1n9c (oleic acid), C20:4 (arachidonic acid) and C16:0 (palmitic acid) constituted the major fractions. However, the relative amount of individual FAs of the TsM parenchyma and granuloma differed from those of TsM CF and swine tissue, which contained enriched C16:0 and a lower amount of C20:4. Saturated FAs were the major constituents in parenchyma and granuloma, 50.4% and 46.1%, respectively. Conversely, monounsaturated FAs were the major constituents of CF and swine tissue, 38.7% and 40.3%, respectively. Our results strongly suggest that host-derived FAs might translocate across the parasite syncytial membrane and be stored in the CF.
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Affiliation(s)
- Seon-Hee Kim
- Department of Molecular Parasitology, Sungkyunkwan University School of Medicine and Center for Molecular Medicine, Samsung Biomedical Research Institute, Suwon 440-746, Republic of Korea
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125
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PDHK-2 deficiency is associated with attenuation of lipase-mediated fat consumption for the increased survival of Caenorhabditis elegans dauers. PLoS One 2012; 7:e41755. [PMID: 22848591 PMCID: PMC3407204 DOI: 10.1371/journal.pone.0041755] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 06/25/2012] [Indexed: 11/19/2022] Open
Abstract
In Caenorhabditis elegans, slow fat consumption has been suggested to contribute to the extension of the survival rate during nutritionally adverse conditions. Here, we investigated the potential role of pyruvate dehydrogenase kinase (PDHK)-2, the C. elegans homolog of mammalian PDK, effects on fat metabolism under nutritional conditions. PDHK-2 was expressed at low levels under well-fed conditions but was highly induced during long-term starvation and in the dauer state. This increase in pdhk-2 expression was regulated by both DAF-16 and NHR-49. Dauer-specific induction of PDHK-2 was abolished upon entry into the post-dauer stage. Interestingly, in the long-term dauer state, stored fat levels were higher in daf-2(e1370);pdhk-2 double mutants than in daf-2(e1370), suggesting a positive relationship between PDHK-2 activity and fat consumption. PDHK-2 deficiency has been shown to lead to greater preservation of residual fats, which would be predicted to contribute to survival during the dauer state. A test of this prediction showed that the survival rates of daf-2(e1370);pdhk-2(tm3075) and daf-2(e1370);pdhk-2(tm3086) double mutants were higher than that of daf-2(e1370), suggesting that loss of either the ATP-binding domain (tm3075) or branched chain keto-acid dehydrogenase kinase domain (tm3086) of PDHK-2 leads to reduced fat consumption and thus favors increased dauer survival. This attenuated fat consumption in the long-term dauer state of C. elegans daf-2 (e1370);pdhk-2 mutants was associated with concomitant down-regulation of the lipases ATGL (adipose triglyceride lipase), HSL (hormone-sensitive lipase), and C07E3.9 (phospholipase). In contrast, PDHK-2 overexpression in wild-type starved worms induced lipase expression and promoted abnormal dauer formation. Thus, we propose that PDHK-2 serves as a molecular bridge, connecting fat metabolism and survival under nutritionally adverse conditions in C. elegans.
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126
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Yuan Y, Kadiyala CS, Ching TT, Hakimi P, Saha S, Xu H, Yuan C, Mullangi V, Wang L, Fivenson E, Hanson RW, Ewing R, Hsu AL, Miyagi M, Feng Z. Enhanced energy metabolism contributes to the extended life span of calorie-restricted Caenorhabditis elegans. J Biol Chem 2012; 287:31414-26. [PMID: 22810224 DOI: 10.1074/jbc.m112.377275] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Caloric restriction (CR) markedly extends life span and improves the health of a broad number of species. Energy metabolism fundamentally contributes to the beneficial effects of CR, but the underlying mechanisms that are responsible for this effect remain enigmatic. A multidisciplinary approach that involves quantitative proteomics, immunochemistry, metabolic quantification, and life span analysis was used to determine how CR, which occurs in the Caenorhabditis elegans eat-2 mutants, modifies energy metabolism of the worm, and whether the observed modifications contribute to the CR-mediated physiological responses. A switch to fatty acid metabolism as an energy source and an enhanced rate of energy metabolism by eat-2 mutant nematodes were detected. Life span analyses validated the important role of these previously unknown alterations of energy metabolism in the CR-mediated longevity of nematodes. As observed in mice, the overexpression of the gene for the nematode analog of the cytosolic form of phosphoenolpyruvate carboxykinase caused a marked extension of the life span in C. elegans, presumably by enhancing energy metabolism via an altered rate of cataplerosis of tricarboxylic acid cycle anions. We conclude that an increase, not a decrease in fuel consumption, via an accelerated oxidation of fuels in the TCA cycle is involved in life span regulation; this mechanism may be conserved across phylogeny.
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Affiliation(s)
- Yiyuan Yuan
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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127
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Yu ZY, Zhang J, Yin DQ. Toxic and recovery effects of copper on Caenorhabditiselegans by various food-borne and water-borne pathways. CHEMOSPHERE 2012; 87:1361-1367. [PMID: 22386928 DOI: 10.1016/j.chemosphere.2012.02.029] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2011] [Revised: 02/02/2012] [Accepted: 02/06/2012] [Indexed: 05/31/2023]
Abstract
Copper pollutions are typical heavy metal contaminations, and their ability to move up food chains urges comprehensive studies on their effects through various pathways. Currently, four exposure pathways were prescribed as food-borne (FB), water-borne plus clean food (WCB), water-food-borne (WFB) and water-borne (WB). Caenorhabditiselegans was chosen as the model organism, and growth statuses, feeding abilities, the amounts of four antioxidant enzymes, and corresponding recovery effects under non-toxic conditions with food and without food were investigated. Based on analysis results, copper concentrations in exposure were significantly influenced by the presence of food and its uptake by C.elegans. Both exposure and recovery effects depended on exposure concentrations and food conditions. For exposure pathways with food, feeding abilities and growth statuses were generally WFB<WCB≤FB (p<0.05). The antioxidant activities were up-regulated in the same order. Meanwhile, the exposure pathway without food (WB) caused non-up-regulated antioxidant activities, and had the best growth statuses. For recoveries with food, growth statuses, feeding abilities and the inductions of the antioxidant enzymes were all WB≈WFB<WCB<FB (p<0.05). For recoveries without food, the order of growth statuses remained WB>FB>WCB>WFB (p<0.05), while the antioxidant activities were all inhibited in a concentration-dependent fashion. In conclusion, contaminated food was the primary exposure pathway, and various pathways caused different responses of C.elegans.
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Affiliation(s)
- Zhen-Yang Yu
- Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
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128
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Hou NS, Taubert S. Function and Regulation of Lipid Biology in Caenorhabditis elegans Aging. Front Physiol 2012; 3:143. [PMID: 22629250 PMCID: PMC3355469 DOI: 10.3389/fphys.2012.00143] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 04/27/2012] [Indexed: 02/02/2023] Open
Abstract
Rapidly expanding aging populations and a concomitant increase in the prevalence of age-related diseases are global health problems today. Over the past three decades, a large body of work has led to the identification of genes and regulatory networks that affect longevity and health span, often benefiting from the tremendous power of genetics in vertebrate and invertebrate model organisms. Interestingly, many of these factors appear linked to lipids, important molecules that participate in cellular signaling, energy metabolism, and structural compartmentalization. Despite the putative link between lipids and longevity, the role of lipids in aging remains poorly understood. Emerging data from the model organism Caenorhabditis elegans suggest that lipid composition may change during aging, as several pathways that influence aging also regulate lipid metabolism enzymes; moreover, some of these enzymes apparently play key roles in the pathways that affect the rate of aging. By understanding how lipid biology is regulated during C. elegans aging, and how it impacts molecular, cellular, and organismal function, we may gain insight into novel ways to delay aging using genetic or pharmacological interventions. In the present review we discuss recent insights into the roles of lipids in C. elegans aging, including regulatory roles played by lipids themselves, the regulation of lipid metabolic enzymes, and the roles of lipid metabolism genes in the pathways that affect aging.
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Affiliation(s)
- Nicole Shangming Hou
- Graduate Program in Cell and Developmental Biology, University of British Columbia Vancouver, BC, Canada
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129
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Temmerman L, Bogaerts A, Meelkop E, Cardoen D, Boerjan B, Janssen T, Schoofs L. A proteomic approach to neuropeptide function elucidation. Peptides 2012; 34:3-9. [PMID: 21920396 DOI: 10.1016/j.peptides.2011.08.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 08/30/2011] [Accepted: 08/30/2011] [Indexed: 12/21/2022]
Abstract
Many of the diverse functions of neuropeptides are still elusive. As they are ideally suited to modulate traditional signaling, their added actions are not always detectable under standard laboratory conditions. The search for function assignment to peptide encoding genes can therefore greatly benefit from molecular information. Specific molecular changes resulting from neuropeptide signaling may direct researchers to yet unknown processes or conditions, for which studying these signaling systems may eventually lead to phenotypic confirmation. Here, we applied gel-based proteomics after pdf-1 neuropeptide gene knockout in the model organism Caenorhabditis elegans. It has previously been described that pdf-1 null mutants display a locomotion defect, being slower and making more turns and reversals than wild type worms. The vertebrate functional homolog of PDF-1, vasocative intestinal peptide (VIP), is known to influence a plethora of processes, which have so far not been investigated for pdf-1. Because proteins represent the actual effectors inside an organism, proteomic analysis can guide our view to novel pdf-1 actions in the nematode worm. Our data show that knocking out pdf-1 results in alteration of levels of proteins involved in fat metabolism, stress resistance and development. This indicates a possible conservation of VIP-like actions for pdf-1 in C. elegans.
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Affiliation(s)
- L Temmerman
- Functional Genomics and Proteomics, Naamsestraat 59, Leuven, Belgium
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130
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Laing ST, Ivens A, Butler V, Ravikumar SP, Laing R, Woods DJ, Gilleard JS. The transcriptional response of Caenorhabditis elegans to Ivermectin exposure identifies novel genes involved in the response to reduced food intake. PLoS One 2012; 7:e31367. [PMID: 22348077 PMCID: PMC3279368 DOI: 10.1371/journal.pone.0031367] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2011] [Accepted: 01/09/2012] [Indexed: 12/02/2022] Open
Abstract
We have examined the transcriptional response of Caenorhabditis elegans following exposure to the anthelmintic drug ivermectin (IVM) using whole genome microarrays and real-time QPCR. Our original aim was to identify candidate molecules involved in IVM metabolism and/or excretion. For this reason the IVM tolerant strain, DA1316, was used to minimise transcriptomic changes related to the phenotype of drug exposure. However, unlike equivalent work with benzimidazole drugs, very few of the induced genes were members of xenobiotic metabolising enzyme families. Instead, the transcriptional response was dominated by genes associated with fat mobilization and fatty acid metabolism including catalase, esterase, and fatty acid CoA synthetase genes. This is consistent with the reduction in pharyngeal pumping, and consequential reduction in food intake, upon exposure of DA1316 worms to IVM. Genes with the highest fold change in response to IVM exposure, cyp-37B1, mtl-1 and scl-2, were comparably up-regulated in response to short–term food withdrawal (4 hr) independent of IVM exposure, and GFP reporter constructs confirm their expression in tissues associated with fat storage (intestine and hypodermis). These experiments have serendipitously identified novel genes involved in an early response of C. elegans to reduced food intake and may provide insight into similar processes in higher organisms.
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Affiliation(s)
- Steven T. Laing
- Faculty of Veterinary Medicine, University of Glasgow, Glasgow, Strathclyde, United Kingdom
| | - Al Ivens
- Fios Genomics Ltd, The Edinburgh Technology Transfer Centre, Edinburgh, Lothian, United Kingdom
| | - Victoria Butler
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Sai P. Ravikumar
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Roz Laing
- Faculty of Veterinary Medicine, University of Glasgow, Glasgow, Strathclyde, United Kingdom
| | - Debra J. Woods
- Research and Development, Pfizer Animal Health, Kalamazoo, Michigan, United States of America
| | - John S. Gilleard
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
- * E-mail:
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131
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Castro C, Sar F, Shaw WR, Mishima M, Miska EA, Griffin JL. A metabolomic strategy defines the regulation of lipid content and global metabolism by Δ9 desaturases in Caenorhabditis elegans. BMC Genomics 2012; 13:36. [PMID: 22264337 PMCID: PMC3398271 DOI: 10.1186/1471-2164-13-36] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 01/20/2012] [Indexed: 11/10/2022] Open
Abstract
Background Caenorhabditis elegans provides a genetically tractable model organism to investigate the network of genes involved in fat metabolism and how regulation is perturbed to produce the complex phenotype of obesity. C. elegans possess the full range of desaturases, including the Δ9 desaturases expressed by fat-5, fat-6 and fat-7. They regulate the biosynthesis of monounsaturated fatty acids, used for the synthesis of lipids including phospholipids, triglycerides and cholesteryl esters. Results Liquid chromatography mass spectrometry (LC-MS), gas chromatography mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy were used to define the metabolome of all the possible knock-outs for the Δ9 desaturases, including for the first time intact lipids. Despite the genes having similar enzymatic roles, excellent discrimination was achievable for all single and viable double mutants highlighting the distinctive roles of fat-6 and fat-7, both expressing steroyl-CoA desaturases. The metabolomic changes extend to aqueous metabolites demonstrating the influence Δ9 desaturases have on regulating global metabolism and highlighting how comprehensive metabolomics is more discriminatory than classically used dyes for fat staining. Conclusions The propagation of metabolic changes across the network of metabolism demonstrates that modification of the Δ9 desaturases places C.elegans into a catabolic state compared with wildtype controls.
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Affiliation(s)
- Cecilia Castro
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK
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132
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Sakamoto T, Inoue T, Otomo Y, Yokomori N, Ohno M, Arai H, Nakagawa Y. Deficiency of cardiolipin synthase causes abnormal mitochondrial function and morphology in germ cells of Caenorhabditis elegans. J Biol Chem 2011; 287:4590-601. [PMID: 22174409 DOI: 10.1074/jbc.m111.314823] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Cardiolipin (CL) is a major membrane phospholipid specifically localized in mitochondria. At the cellular level, CL has been shown to have a role in mitochondrial energy production, mitochondrial membrane dynamics, and the triggering of apoptosis. However, the in vivo role of CL in multicellular organisms is largely unknown. In this study, by analyzing deletion mutants of a CL synthase gene (crls-1) in Caenorhabditis elegans, we demonstrated that CL depletion selectively caused abnormal mitochondrial function and morphology in germ cells but not in somatic cell types such as muscle cells. crls-1 mutants reached adulthood but were sterile with reduced germ cell proliferation and impaired oogenesis. In the gonad of crls-1 mutants, mitochondrial membrane potential was significantly decreased, and the structure of the mitochondrial cristae was disrupted. Contrary to the abnormalities in the gonad, somatic tissues in crls-1 mutants appeared normal with respect to cell proliferation, mitochondrial function, and mitochondrial morphology. Increased susceptibility to CL depletion in germ cells was also observed in mutants of phosphatidylglycerophosphate synthase, an enzyme responsible for producing phosphatidylglycerol, a precursor phospholipid of CL. We propose that the contribution of CL to mitochondrial function and morphology is different among the cell types in C. elegans.
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Affiliation(s)
- Taro Sakamoto
- School of Pharmacy, Kitasato University, Tokyo 108-8641, Japan.
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Lee BH, Liu J, Wong D, Srinivasan S, Ashrafi K. Hyperactive neuroendocrine secretion causes size, feeding, and metabolic defects of C. elegans Bardet-Biedl syndrome mutants. PLoS Biol 2011; 9:e1001219. [PMID: 22180729 PMCID: PMC3236739 DOI: 10.1371/journal.pbio.1001219] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 11/02/2011] [Indexed: 12/16/2022] Open
Abstract
Bardet-Biedl syndrome, BBS, is a rare autosomal recessive disorder with clinical presentations including polydactyly, retinopathy, hyperphagia, obesity, short stature, cognitive impairment, and developmental delays. Disruptions of BBS proteins in a variety of organisms impair cilia formation and function and the multi-organ defects of BBS have been attributed to deficiencies in various cilia-associated signaling pathways. In C. elegans, bbs genes are expressed exclusively in the sixty ciliated sensory neurons of these animals and bbs mutants exhibit sensory defects as well as body size, feeding, and metabolic abnormalities. Here we show that in contrast to many other cilia-defective mutants, C. elegans bbs mutants exhibit increased release of dense-core vesicles and organism-wide phenotypes associated with enhanced activities of insulin, neuropeptide, and biogenic amine signaling pathways. We show that the altered body size, feeding, and metabolic abnormalities of bbs mutants can be corrected to wild-type levels by abrogating the enhanced secretion of dense-core vesicles without concomitant correction of ciliary defects. These findings expand the role of BBS proteins to the regulation of dense-core-vesicle exocytosis and suggest that some features of Bardet-Biedl Syndrome may be caused by excessive neuroendocrine secretion. Bardet-Biedl syndrome, BBS, is a rare human genetic disease caused by mutations in many genes. The BBS phenotype is very complex; it is principally characterized by early-onset obesity, progressive blindness, extra digits on the hands and feet, and renal problems. BBS patients may also suffer from developmental delay, learning disabilities, diabetes, and loss of the sense of smell. This complexity suggests that BBS proteins function in a variety of tissues, causing defects in many organs. A unifying theme for the diverse features of BBS emerged when BBS genes were identified and their protein products were found to function in the cilium, a sensory structure found in many cell types. Since then, the various manifestations of BBS have been attributed to the loss of ciliary function in the corresponding tissues. This notion was also supported by the finding that mutations in several genes required for proper cilia formation and function reproduce some of the features seen in BBS patients. Here, we have further investigated the defects found in Caenorhabditis elegans strains carrying mutations in BBS genes (bbs mutants). We find that not only do they display sensory deficits associated with loss of ciliary function, but they also exhibit increased release of multiple peptide and biogenic amine hormones contained in dense-core vesicles of ciliated sensory neurons. Importantly, limiting this excessive hormonal release without correcting the ciliary defects of bbs mutants was sufficient to restore normal body size, feeding, and metabolism to these mutants. Moreover, we show that although non-bbs ciliary mutations can mimic some of the phenotypes of bbs mutants, these effects can be attributed to distinct spatial and molecular mechanisms. Our findings indicate that C. elegans bbs mutants exhibit features of both ciliary and endocrine defects and suggest that some of the clinical manifestations of human BBS may result from excessive endocrine activity, independently of the loss of ciliary function.
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Affiliation(s)
- Brian H. Lee
- Department of Physiology and the UCSF Diabetes Center, University of California, San Francisco, San Francisco, California, United States of America
| | - Jason Liu
- Department of Physiology and the UCSF Diabetes Center, University of California, San Francisco, San Francisco, California, United States of America
| | - Daisy Wong
- Department of Physiology and the UCSF Diabetes Center, University of California, San Francisco, San Francisco, California, United States of America
| | - Supriya Srinivasan
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Kaveh Ashrafi
- Department of Physiology and the UCSF Diabetes Center, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail:
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Zielke N, Kim KJ, Tran V, Shibutani ST, Bravo MJ, Nagarajan S, van Straaten M, Woods B, von Dassow G, Rottig C, Lehner CF, Grewal SS, Duronio RJ, Edgar BA. Control of Drosophila endocycles by E2F and CRL4(CDT2). Nature 2011; 480:123-7. [PMID: 22037307 PMCID: PMC3330263 DOI: 10.1038/nature10579] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Accepted: 09/21/2011] [Indexed: 12/20/2022]
Abstract
Endocycles are variant cell cycles comprised of DNA Synthesis (S)- and Gap (G)- phases but lacking mitosis1,2. Such cycles facilitate post-mitotic growth in many invertebrate and plant cells, and are so ubiquitous that they may account for up to half the world’s biomass3,4. DNA replication in endocycling Drosophila cells is triggered by Cyclin E/Cyclin Dependent Kinase 2 (CycE/Cdk2), but this kinase must be inactivated during each G-phase to allow the assembly of pre-Replication Complexes (preRCs) for the next S-phase5,6. How CycE/Cdk2 is periodically silenced to allow re-replication has not been established. Here, using genetic tests in parallel with computational modeling, we show that Drosophila’s endocycles are driven by a molecular oscillator in which the E2F1 transcription factor promotes CycE expression and S-phase initiation, S-phase then activates the CRL4Cdt2 ubiquitin ligase, and this in turn mediates the destruction of E2F17. We propose that it is the transient loss of E2F1 during S-phases that creates the window of low Cdk activity required for preRC formation. In support of this model over-expressed E2F1 accelerated endocycling, whereas a stabilized variant of E2F1 blocked endocycling by de-regulating target genes including CycE, as well as Cdk1 and mitotic Cyclins. Moreover, we find that altering cell growth by changing nutrition or TOR signaling impacts E2F1 translation, thereby making endocycle progression growth-dependent. Many of the regulatory interactions essential to this novel cell cycle oscillator are conserved in animals and plants1,2,8, suggesting that elements of this mechanism act in most growth-dependent cell cycles.
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Affiliation(s)
- Norman Zielke
- German Cancer Research Center (DKFZ)-Zentrum für Molekulare Biologie der Universität Heidelberg Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
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135
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Abstract
Sterol metabolites are critical signaling molecules that regulate metabolism, development, and homeostasis. Oxysterols, bile acids (BAs), and steroids work primarily through cognate sterol-responsive nuclear hormone receptors to control these processes through feed-forward and feedback mechanisms. These signaling pathways are conserved from simple invertebrates to mammals. Indeed, results from various model organisms have yielded fundamental insights into cholesterol and BA homeostasis, lipid and glucose metabolism, protective mechanisms, tissue differentiation, development, reproduction, and even aging. Here, we review how sterols act through evolutionarily ancient mechanisms to control these processes.
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Affiliation(s)
- Joshua Wollam
- Department of Molecular and Cellular Biology, Huffington Center on Aging, Baylor College of Medicine, Houston, Texas 77030, USA
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136
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Tissue- and paralogue-specific functions of acyl-CoA-binding proteins in lipid metabolism in Caenorhabditis elegans. Biochem J 2011; 437:231-41. [PMID: 21539519 DOI: 10.1042/bj20102099] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
ACBP (acyl-CoA-binding protein) is a small primarily cytosolic protein that binds acyl-CoA esters with high specificity and affinity. ACBP has been identified in all eukaryotic species, indicating that it performs a basal cellular function. However, differential tissue expression and the existence of several ACBP paralogues in many eukaryotic species indicate that these proteins serve distinct functions. The nematode Caenorhabditis elegans expresses seven ACBPs: four basal forms and three ACBP domain proteins. We find that each of these paralogues is capable of complementing the growth of ACBP-deficient yeast cells, and that they exhibit distinct temporal and tissue expression patterns in C. elegans. We have obtained loss-of-function mutants for six of these forms. All single mutants display relatively subtle phenotypes; however, we find that functional loss of ACBP-1 leads to reduced triacylglycerol (triglyceride) levels and aberrant lipid droplet morphology and number in the intestine. We also show that worms lacking ACBP-2 show a severe decrease in the β-oxidation of unsaturated fatty acids. A quadruple mutant, lacking all basal ACBPs, is slightly developmentally delayed, displays abnormal intestinal lipid storage, and increased β-oxidation. Collectively, the present results suggest that each of the ACBP paralogues serves a distinct function in C. elegans.
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137
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Fredens J, Engholm-Keller K, Giessing A, Pultz D, Larsen MR, Højrup P, Møller-Jensen J, Færgeman NJ. Quantitative proteomics by amino acid labeling in C. elegans. Nat Methods 2011; 8:845-7. [PMID: 21874006 DOI: 10.1038/nmeth.1675] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Accepted: 07/26/2011] [Indexed: 01/01/2023]
Abstract
We demonstrate labeling of Caenorhabditis elegans with heavy isotope-labeled lysine by feeding them with heavy isotope-labeled Escherichia coli. Using heavy isotope-labeled worms and quantitative proteomics methods, we identified several proteins that are regulated in response to loss or RNAi-mediated knockdown of the nuclear hormone receptor 49 in C. elegans. The combined use of quantitative proteomics and selective gene knockdown is a powerful tool for C. elegans biology.
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Affiliation(s)
- Julius Fredens
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
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138
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Kimble J. Molecular regulation of the mitosis/meiosis decision in multicellular organisms. Cold Spring Harb Perspect Biol 2011; 3:a002683. [PMID: 21646377 PMCID: PMC3140684 DOI: 10.1101/cshperspect.a002683] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A major step in the journey from germline stem cell to differentiated gamete is the decision to leave the mitotic cell cycle and begin progression through the meiotic cell cycle. Over the past decade, molecular regulators of the mitosis/meiosis decision have been discovered in most of the major model multicellular organisms. Historically, the mitosis/meiosis decision has been closely linked with controls of germline self-renewal and the sperm/egg decision, especially in nematodes and mice. Molecular explanations of those linkages clarify our understanding of this fundamental germ cell decision, and unifying themes have begun to emerge. Although the complete circuitry of the decision is not known in any organism, the recent advances promise to impact key issues in human reproduction and agriculture.
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Affiliation(s)
- Judith Kimble
- Howard Hughes Medical Institute, Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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139
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Pukkila-Worley R, Ausubel FM, Mylonakis E. Candida albicans infection of Caenorhabditis elegans induces antifungal immune defenses. PLoS Pathog 2011; 7:e1002074. [PMID: 21731485 PMCID: PMC3121877 DOI: 10.1371/journal.ppat.1002074] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 04/06/2011] [Indexed: 12/31/2022] Open
Abstract
Candida albicans yeast cells are found in the intestine of most humans, yet this opportunist can invade host tissues and cause life-threatening infections in susceptible individuals. To better understand the host factors that underlie susceptibility to candidiasis, we developed a new model to study antifungal innate immunity. We demonstrate that the yeast form of C. albicans establishes an intestinal infection in Caenorhabditis elegans, whereas heat-killed yeast are avirulent. Genome-wide, transcription-profiling analysis of C. elegans infected with C. albicans yeast showed that exposure to C. albicans stimulated a rapid host response involving 313 genes (124 upregulated and 189 downregulated, ∼1.6% of the genome) many of which encode antimicrobial, secreted or detoxification proteins. Interestingly, the host genes affected by C. albicans exposure overlapped only to a small extent with the distinct transcriptional responses to the pathogenic bacteria Pseudomonas aeruginosa or Staphylococcus aureus, indicating that there is a high degree of immune specificity toward different bacterial species and C. albicans. Furthermore, genes induced by P. aeruginosa and S. aureus were strongly over-represented among the genes downregulated during C. albicans infection, suggesting that in response to fungal pathogens, nematodes selectively repress the transcription of antibacterial immune effectors. A similar phenomenon is well known in the plant immune response, but has not been described previously in metazoans. Finally, 56% of the genes induced by live C. albicans were also upregulated by heat-killed yeast. These data suggest that a large part of the transcriptional response to C. albicans is mediated through “pattern recognition,” an ancient immune surveillance mechanism able to detect conserved microbial molecules (so-called pathogen-associated molecular patterns or PAMPs). This study provides new information on the evolution and regulation of the innate immune response to divergent pathogens and demonstrates that nematodes selectively mount specific antifungal defenses at the expense of antibacterial responses. Despite being a part of the normal flora of healthy individuals, Candida albicans is the most common fungal pathogen of humans and can cause infections that are associated with staggeringly high mortality rates. Here we devise a model for the study of the host immune response to C. albicans infection using the nematode C. elegans. We found that infection with the yeast form of C. albicans induces rapid and robust transcriptional changes in C. elegans. Analyses of these differentially regulated genes indicate that the nematode mounts antifungal defenses that are remarkably distinct from the host responses to pathogenic bacteria and that the nematode recognizes components possessed by heat-killed C. albicans to initiate this response. Interestingly, during infection with a pathogenic fungus, the nematode downregulates antibacterial immune response genes, which may reflect an evolutionary tradeoff between bacterial and fungal defense.
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Affiliation(s)
- Read Pukkila-Worley
- Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Frederick M. Ausubel
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (FMA); (EM)
| | - Eleftherios Mylonakis
- Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail: (FMA); (EM)
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140
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Xu M, Joo HJ, Paik YK. Novel functions of lipid-binding protein 5 in Caenorhabditis elegans fat metabolism. J Biol Chem 2011; 286:28111-8. [PMID: 21697096 DOI: 10.1074/jbc.m111.227165] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The lipid-binding protein (LBP) family is conserved from Caenorhabditis elegans to mammals and essential for fatty acid homeostasis. RNAi-mediated knockdown of nine C. elegans lbp family members revealed that lbp-5 regulates fat accumulation. C. elegans LBP-5 bound directly to various fatty acids with varying affinities. lbp-5 expression in nhr-49(nr2041) worms was much lower than in N2 worms. Nhr-49 transcriptional activity also decreased with lbp-5 deletion, suggesting that they may work together as functional partners in fat metabolism. In support of this notion, LBP-5 translocated into nuclei, where it appeared to influence C. elegans NHR-49 target genes involved in energy metabolism. Interestingly, LBP-5 is required for stearic acid-induced transcription of NHR-49 target genes. Thus, this knowledge could help identify therapeutic targets to treat obesity and diseases associated with nematode-host interactions.
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Affiliation(s)
- Mo Xu
- Department of Biochemistry and Biomedical Science, World Class University Program, College of Life Science and Biotechnology, Yonsei Proteome Research Center, Yonsei University, Seoul 120-749, Korea
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141
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Mendenhall AR, Wu D, Park SK, Cypser JR, Tedesco PM, Link CD, Phillips PC, Johnson TE. Genetic dissection of late-life fertility in Caenorhabditis elegans. J Gerontol A Biol Sci Med Sci 2011; 66:842-54. [PMID: 21622982 DOI: 10.1093/gerona/glr089] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The large post-reproductive life span reported for the free-living hermaphroditic nematode, Caenorhabditis elegans, which lives for about 10 days after its 5-day period of self-reproduction, seems at odds with evolutionary theory. Species with long post-reproductive life spans such as mammals are sometimes explained by a need for parental care or transfer of information. This does not seem a suitable explanation for C elegans. Previous reports have shown that C elegans can regain fertility when mated after the self-fertile period but did not report the functional limits. Here, we report the functional life span of the C elegans germ line when mating with males. We show that C elegans can regain fertility late in life (significantly later than in previous reports) and that the end of this period corresponds quite well to its 3-week total life span. Genetic analysis reveals that late-life fertility is controlled by conserved pathways involved with aging and dietary restriction.
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142
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Aarnio V, Lehtonen M, Storvik M, Callaway JC, Lakso M, Wong G. Caenorhabditis Elegans Mutants Predict Regulation of Fatty Acids and Endocannabinoids by the CYP-35A Gene Family. Front Pharmacol 2011; 2:12. [PMID: 21687507 PMCID: PMC3108558 DOI: 10.3389/fphar.2011.00012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Accepted: 02/28/2011] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Cytochrome P450s (CYPs) are mono-oxygenases that metabolize endogenous compounds, such as fatty acids and lipid signaling molecules, and furthermore have a role in metabolism of xenobiotics. In order to investigate the role of CYP genes in fat metabolism at the molecular level, four Caenorhabditis elegans mutants lacking functional CYP-35A1, CYP-35A2, CYP-35A4, and CYP-35A5 were characterized. Relative amounts of fatty acids, as well as endocannabinoids, which regulate weight gain and accumulation of fats in mammals, were measured while fat contents in worms were visualized using Oil-Red-O staining. RESULTS The cyp-35A1 and cyp-35A5 mutants had a significantly lower intestinal fat content than wild-type animals, whereas cyp-35A2 and cyp-35A4 mutants appeared normal. The overall fatty acid compositions of CYP mutants did not alter dramatically, although modest but significant changes were observed. cyp-35A1 and cyp-35A5 mutants had significantly higher levels of C18:1n7 and lower C18:2n6c. All four mutants had higher relative amounts of C18:1n7 than the wild-type. In the cyp-35A5 mutant, the levels of the endocannabinoid anandamide were found to be 4.6-fold higher than in wild-type. Several fatty acid synthesis genes were over-expressed in cyp-35A1 including fat-2. Feeding oleic or elaidic triglycerides to wild-type animals demonstrated that cyp-35A1 transcriptional levels are insensitive to environmental exposure of these fats, while cyp-35A2, cyp-35A4, and cyp-35A5 were significantly down regulated. CONCLUSION These results demonstrate a dynamic role for CYP-35A subfamily members in maintaining the diversity of fatty acid profiles in C. elegans, and more generally highlight the importance of CYPs in generating both structural and signaling fatty acid functions in other organisms.
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Affiliation(s)
- Vuokko Aarnio
- Functional Genomics and Bioinformatics Laboratory, Department of Biosciences and Department of Neurobiology, A. I. Virtanen Institute, Biocenter Finland, University of Eastern Finland Kuopio, Finland
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143
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Lemieux GA, Liu J, Mayer N, Bainton RJ, Ashrafi K, Werb Z. A whole-organism screen identifies new regulators of fat storage. Nat Chem Biol 2011; 7:206-13. [PMID: 21390037 PMCID: PMC3076723 DOI: 10.1038/nchembio.534] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Accepted: 01/24/2011] [Indexed: 01/08/2023]
Abstract
The regulation of energy homeostasis integrates diverse biological processes ranging from behavior to metabolism and is linked fundamentally to numerous disease states. To identify new molecules that can bypass homeostatic compensatory mechanisms of energy balance in intact animals, we screened for small-molecule modulators of Caenorhabditis elegans fat content. We report on several molecules that modulate fat storage without obvious deleterious effects on feeding, growth and reproduction. A subset of these compounds also altered fat storage in mammalian and insect cell culture. We found that one of the newly identified compounds exerts its effects in C. elegans through a pathway that requires previously undescribed functions of an AMP-activated kinase catalytic subunit and a transcription factor previously unassociated with fat regulation. Thus, our strategy identifies small molecules that are effective within the context of intact animals and reveals relationships between new pathways that operate across phyla to influence energy homeostasis.
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Affiliation(s)
- George A Lemieux
- Department of Anatomy, University of California, San Francisco, San Francisco, California, USA
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144
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Taubert S, Ward JD, Yamamoto KR. Nuclear hormone receptors in nematodes: evolution and function. Mol Cell Endocrinol 2011; 334:49-55. [PMID: 20438802 PMCID: PMC3042524 DOI: 10.1016/j.mce.2010.04.021] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2010] [Revised: 04/18/2010] [Accepted: 04/24/2010] [Indexed: 11/16/2022]
Abstract
Nuclear hormone receptors (NHRs) are proteins that regulate gene expression in response to developmental, environmental, and nutritional signals. The activity of some NHRs is selectively and reversibly modulated by small molecular weight compounds. However, for others - termed "orphan" receptors - no such ligands have (yet) been identified, and at least some NHRs may lack natural ligands. NHRs exhibit a stereotyped architecture, with conserved N-terminal DNA-binding domains (DBDs) and more variable C-terminal ligand-binding domains (LBDs). NHRs control the transcription of remarkably diverse and specific gene networks, apparently by integrating multiple regulatory inputs that interact with distinct receptor surfaces; these inputs include small molecule ligands, transcriptional coregulators, and response elements, the genomic sites to which the receptors bind. NHRs comprise an ancient superfamily found in all metazoans, and recent findings have revealed NHR-like regulatory factors in fungi. Here, we consider NHR function and evolution in nematodes, roundworms that inhabit terrestrial, marine, and freshwater habitats; we focus in particular on the well-established experimental organism Caenorhabditis elegans. Interestingly, the C. elegans genome encodes a massively expanded NHR family; we speculate that some of the multiple physiological activities governed by individual mammalian NHRs may be distributed among multiple members of the C. elegans family, potentially focusing and simplifying functional analyses. Accordingly, investigations of relevant NHR cofactors, ligands, and response elements might also prove to be simpler; moreover, the abbreviated intergenic regions of the C. elegans genome will facilitate the assignment of response elements to target genes. Finally, the growing interest in medically relevant nematodes is providing novel insights into the function and evolution of NHRs.
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Affiliation(s)
- Stefan Taubert
- Department of Medical Genetics, University of British Columbia; Centre for Molecular Medicine and Therapeutics; and Child & Family Research Institute, Vancouver, BC, Canada
| | - Jordan D. Ward
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA, USA
| | - Keith R. Yamamoto
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA, USA
- Corresponding author: UCSF, 600 16 St, GH-S574, San Francisco CA 94143-2280; Phone: +1 (415) 476-8445;
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145
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Reisner K, Lehtonen M, Storvik M, Jantson T, Lakso M, Callaway JC, Wong G. Trans fat diet causes decreased brood size and shortened lifespan in Caenorhabditis elegans delta-6-desaturase mutant fat-3. J Biochem Mol Toxicol 2011; 25:269-79. [PMID: 21308896 DOI: 10.1002/jbt.20386] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 11/21/2010] [Accepted: 11/24/2010] [Indexed: 01/04/2023]
Abstract
Trans-fatty acids (TFAs) enter the diet through industrial processes and can cause adverse human health effects. The present study was aimed to examine the effects of dietary cis- and trans-fatty acids on the model organism Caenorhabditis elegans. Cis- or trans-18:1n9 triglycerides (25 μM) caused no apparent changes in the numbers of viable progeny of wild-type N2 animals. However, in fat-3 mutants lacking delta-6-desaturase, the trans-isomer caused modest decreases in lifespan and progeny after three generations. Long-chain polyunsaturated fatty acids (PUFA) profiles were significantly altered in fat-3 mutants compared to wild type but were not altered after exposure to dietary cis- or trans-18:1n9. Genome-wide expression analysis of fat-3 mutants revealed hundreds of changes. Several genes involved in fat metabolism (acs-2, fat-7, mdt-15) were significantly increased by cis- or trans-18:1n9 without discrimination between isomers. These results provide support for the hypothesis that dietary trans fats are detrimental to development and aging.
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Affiliation(s)
- Kaja Reisner
- Department of Biosciences, University of Eastern Finland, Kuopio 70211, Finland
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146
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Shin H, Lee H, Fejes AP, Baillie DL, Koo HS, Jones SJ. Gene expression profiling of oxidative stress response of C. elegans aging defective AMPK mutants using massively parallel transcriptome sequencing. BMC Res Notes 2011; 4:34. [PMID: 21303547 PMCID: PMC3045954 DOI: 10.1186/1756-0500-4-34] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 02/08/2011] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND A strong association between stress resistance and longevity in multicellular organisms has been established as many mutations that extend lifespan also show increased resistance to stress. AAK-2, the C. elegans homolog of an alpha subunit of AMP-activated protein kinase (AMPK) is an intracellular fuel sensor that regulates cellular energy homeostasis and functions in stress resistance and lifespan extension. FINDINGS Here, we investigated global transcriptional responses of aak-2 mutants to oxidative stress and in turn identified potential downstream targets of AAK-2 involved in stress resistance in C. elegans. We employed massively parallel Illumina sequencing technology and performed comprehensive comparative transcriptome analysis. Specifically, we compared the transcriptomes of aak-2 and wild type animals under normal conditions and conditions of induced oxidative stress. This research has presented a snapshot of genome-wide transcriptional activities that take place in C. elegans in response to oxidative stress both in the presence and absence of AAK-2. CONCLUSIONS The analysis presented in this study has enabled us to identify potential genes involved in stress resistance that may be either directly or indirectly under the control of AAK-2. Furthermore, we have extended our current knowledge of general defense responses of C. elegans against oxidative stress supporting the function for AAK-2 in inhibition of biosynthetic processes, especially lipid synthesis, under oxidative stress and transcriptional regulation of genes involved in reproductive processes.
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Affiliation(s)
- Heesun Shin
- Genome Sciences Centre, BC Cancer Agency, Suite 100 570 West 7th Avenue, Vancouver, British Columbia, Canada V5Z 4S6.
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147
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Powolny AA, Singh SV, Melov S, Hubbard A, Fisher AL. The garlic constituent diallyl trisulfide increases the lifespan of C. elegans via skn-1 activation. Exp Gerontol 2011; 46:441-52. [PMID: 21296648 DOI: 10.1016/j.exger.2011.01.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 01/25/2011] [Accepted: 01/26/2011] [Indexed: 02/07/2023]
Abstract
Medicinal benefits of Allium vegetables, such as garlic, have been noted throughout recorded history, including protection against cancer and cardiovascular disease. We now demonstrate that garlic constituent diallyl trisulfide (DATS) increases longevity of Caenorhabditis elegans by affecting the skn-1 pathway. Treatment of worms with 5-10 μM DATS increased worm mean lifespan even when treatment is started during young adulthood. To explore the mechanisms involved in the DATS-mediated increase in longevity, we treated daf-2, daf-16, and eat-2 mutants and found that DATS increased the lifespan of daf-2 and daf-16 mutants, but not the eat-2 mutants. Microarray experiments demonstrated that a number of genes regulated by oxidative stress and the skn-1 transcription factor were also changed by DATS treatment. Consistently, DATS treatment leads to the induction of the skn-1 target gene gst-4, and this induction was dependent on skn-1. We also found that the effects of DATS on worm lifespan depend on skn-1 activity in both in the intestine and ASI neurons. Together our data suggest that DATS is able to increase worm lifespan by enhancing the function of the pro-longevity transcription factor skn-1.
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Affiliation(s)
- Anna A Powolny
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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Aitlhadj L, Ávila DS, Benedetto A, Aschner M, Stürzenbaum SR. Environmental exposure, obesity, and Parkinson's disease: lessons from fat and old worms. ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:20-8. [PMID: 20797931 PMCID: PMC3018495 DOI: 10.1289/ehp.1002522] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Accepted: 08/25/2010] [Indexed: 05/02/2023]
Abstract
BACKGROUND A common link has been exposed, namely, that metal exposure plays a role in obesity and in Parkinson's disease (PD). This link may help to elucidate mechanisms of neurotoxicity. OBJECTIVE We reviewed the utility of the nematode, Caenorhabditis elegans, as a model organism to study neurodegeneration in obesity and Parkinson's disease (PD), with an emphasis on the neurotransmitter, dopamine (DA). DATA SOURCES A PubMed literature search was performed using the terms "obesity" and any of the following: "C. elegans," "central nervous system," "neurodegeneration," "heavy metals," "dopamine" or "Parkinson's disease." We reviewed the identified studies, including others cited therein, to summarize the current evidence of neurodegeneration in obesity and PD, with an emphasis on studies carried out in C. elegans and environmental toxins in the etiology of both diseases. DATA EXTRACTION AND DATA SYNTHESIS Heavy metals and DA have both been linked to diet-induced obesity, which has led to the notion that the mechanism of environmentally induced neurodegeneration in PD may also apply to obesity. C. elegans has been instrumental in expanding our mechanism-based knowledge of PD, and this species is emerging as a good model of obesity. With well-established toxicity and neurogenetic assays, it is now feasible to explore the putative link between metal- and chemical-induced neurodegeneration. CONCLUSIONS One side effect of an aging population is an increase in the prevalence of obesity, metabolic disorders, and neurodegenerative orders, diseases that are likely to co-occur. Environmental toxins, especially heavy metals, may prove to be a previously neglected part of the puzzle.
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Affiliation(s)
- Layla Aitlhadj
- King’s College London, Pharmaceutical Science Division, London, United Kingdom
| | - Daiana Silva Ávila
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Alexandre Benedetto
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Michael Aschner
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Arda HE, Taubert S, MacNeil LT, Conine CC, Tsuda B, Van Gilst M, Sequerra R, Doucette-Stamm L, Yamamoto KR, Walhout AJM. Functional modularity of nuclear hormone receptors in a Caenorhabditis elegans metabolic gene regulatory network. Mol Syst Biol 2010; 6:367. [PMID: 20461074 PMCID: PMC2890327 DOI: 10.1038/msb.2010.23] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 03/26/2010] [Indexed: 12/15/2022] Open
Abstract
We present the first gene regulatory network (GRN) that pertains to post-developmental gene expression. Specifically, we mapped a transcription regulatory network of Caenorhabditis elegans metabolic gene promoters using gene-centered yeast one-hybrid assays. We found that the metabolic GRN is enriched for nuclear hormone receptors (NHRs) compared with other gene-centered regulatory networks, and that these NHRs organize into functional network modules. The NHR family has greatly expanded in nematodes; C. elegans has 284 NHRs, whereas humans have only 48. We show that the NHRs in the metabolic GRN have metabolic phenotypes, suggesting that they do not simply function redundantly. The mediator subunit MDT-15 preferentially interacts with NHRs that occur in the metabolic GRN. We describe an NHR circuit that responds to nutrient availability and propose a model for the evolution and organization of NHRs in C. elegans metabolic regulatory networks.
Physical and/or regulatory interactions between transcription factors (TFs) and their target genes are essential to establish body plans of multicellular organisms during development, and these interactions have been studied extensively in the context of GRNs. The precise control of differential gene expression is also of critical importance to maintain physiological homeostasis, and many metabolic disorders such as obesity and diabetes coincide with substantial changes in gene expression. Much work has focused on the GRNs that control metazoan development; however, the design principles and organization of the GRNs that control systems physiology remain largely unexplored. In this study, we present the first gene-centered GRN that includes ∼70 genes involved in C. elegans metabolism and physiology, 100 TFs and more than 500 protein–DNA interactions between them. The resulting metabolic GRN is enriched for NHRs, compared with other gene-centered regulatory networks. NHRs are well-known regulators of lipid meta-qj;bolism in mammals. The transcriptional activity of NHRs can be modified by diffusible ligands, which allows these TFs to function as molecular sensors and rapidly alter the expression of their target genes. Interestingly, NHRs comprise the largest family of TFs in nematodes; the C. elegans genome encodes 284 NHRs, most of which are uncharacterized. Furthermore, their organization in GRNs has not yet been investigated. In our study, we show that the C. elegans NHRs that we retrieved in the metabolic GRN organize into network modules, and that most of these NHRs function to maintain lipid homeostasis in the nematode. Interestingly, network modularity has been proposed to facilitate rapid and robust changes in gene expression. Our results suggest that the C. elegans metabolic GRN may have evolved by combining NHR family expansion with the specific modular wiring of NHRs to enable the rapid adaptation of the animal to different environmental cues. NHRs can interact with transcriptional cofactors such as chromatin remodeling complexes and Mediator components. For instance, the C. elegans Mediator subunit, MDT-15, can interact with NHR-49 to regulate the expression of its target genes. To find all the TFs that MDT-15 can interact with, we performed systematic yeast two-hybrid assays with MDT-15 versus 755 full-length TFs. We found that MDT-15 preferentially associates with NHRs, and specifically with those NHRs that confer a metabolic phenotype and that occur in the metabolic GRN. This illustrates the central role of MDT-15 in the regulation of metabolic gene expression. Using a variety of genetic and biochemical approaches, we characterized NHR-86 in more detail. NHR-86 participates in one of the two NHR modules, and has a high-flux capacity; that is it has both a high incoming and a high outgoing degree. We obtained an nhr-86 mutant and generated an NHR-86 antibody, and showed that NHR-86 functions as an auto-repressor in vivo and that nhr-86 mutant animals store abnormally high levels of body fat. Finally, we discovered a novel NHR circuit that responds to nutrient availability. In this circuit NHR-45 regulates the activity of nhr-178 promoter in two distinct physiologically important tissues: the intestine and the hypodermis. Both of these NHRs are required to maintain lipid homeostasis in C. elegans. The expression of nhr-178 is responsive to the nutritional status of the animal, which switches between ON and OFF states in the hypodermis. We found that NHR-45 activity is necessary to control this switch in the hypodermis. Interestingly, NHR-45 has opposite effects on the activity of the nhr-178 promoter in these tissues: NHR-45 activates this promoter in the intestine, but represses it in the hypodermis. Altogether our study leads to a model in which the expansion of the NHR family, TFs that have the capacity to act as fast molecular sensors, is combined with a modular network organization to enable rapid and robust responses to various environmental cues. Gene regulatory networks (GRNs) provide insights into the mechanisms of differential gene expression at a systems level. GRNs that relate to metazoan development have been studied extensively. However, little is still known about the design principles, organization and functionality of GRNs that control physiological processes such as metabolism, homeostasis and responses to environmental cues. In this study, we report the first experimentally mapped metazoan GRN of Caenorhabditis elegans metabolic genes. This network is enriched for nuclear hormone receptors (NHRs). The NHR family has greatly expanded in nematodes: humans have 48 NHRs, but C. elegans has 284, most of which are uncharacterized. We find that the C. elegans metabolic GRN is highly modular and that two GRN modules predominantly consist of NHRs. Network modularity has been proposed to facilitate a rapid response to different cues. As NHRs are metabolic sensors that are poised to respond to ligands, this suggests that C. elegans GRNs evolved to enable rapid and adaptive responses to different cues by a concurrence of NHR family expansion and modular GRN wiring.
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Affiliation(s)
- H Efsun Arda
- Program in Gene Function and Expression and Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
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Yamawaki TM, Berman JR, Suchanek-Kavipurapu M, McCormick M, Gaglia MM, Lee SJ, Kenyon C. The somatic reproductive tissues of C. elegans promote longevity through steroid hormone signaling. PLoS Biol 2010; 8. [PMID: 20824162 PMCID: PMC2930862 DOI: 10.1371/journal.pbio.1000468] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Accepted: 07/20/2010] [Indexed: 01/09/2023] Open
Abstract
Removal of the germ cells of C. elegans extends lifespan in part because signals from the somatic reproductive tissues activate the nuclear hormone receptor DAF-12. In Caenorhabditis elegans and Drosophila melanogaster, removing the germline precursor cells increases lifespan. In worms, and possibly also in flies, this lifespan extension requires the presence of somatic reproductive tissues. How the somatic gonad signals other tissues to increase lifespan is not known. The lifespan increase triggered by loss of the germ cells is known to require sterol hormone signaling, as reducing the activity of the nuclear hormone receptor DAF-12, or genes required for synthesis of the DAF-12 ligand dafachronic acid, prevents germline loss from extending lifespan. In addition to sterol signaling, the FOXO transcription factor DAF-16 is required to extend lifespan in animals that lack germ cells. DAF-12/NHR is known to assist with the nuclear accumulation of DAF-16/FOXO in these animals, yet we find that loss of DAF-12/NHR has little or no effect on the expression of at least some DAF-16/FOXO target genes. In this study, we show that the DAF-12-sterol signaling pathway has a second function to activate a distinct set of genes and extend lifespan in response to the somatic reproductive tissues. When germline-deficient animals lacking somatic reproductive tissues are given dafachronic acid, their expression of DAF-12/NHR-dependent target genes is restored and their lifespan is increased. Together, our findings indicate that in C. elegans lacking germ cells, the somatic reproductive tissues promote longevity via steroid hormone signaling to DAF-12. Reproductive tissues are known to generate important intercellular signals. For example, in mammals, the reproductive tissues produce steroid hormones such as estrogen and testosterone that have profound effects on development and physiology. Studies of the nematode C. elegans and other organisms have shown that the reproductive system can also affect the rate at which an animal ages. Removal of C. elegans' germ cells extends lifespan but this effect is not simply due to sterility, as removal of both the somatic reproductive tissues and the germ cells does not extend lifespan. Instead, loss of the germ cells extends lifespan by activating a pathway that requires input from the somatic gonad. In this study, we demonstrate that the somatic reproductive tissues promote longevity by controlling the activity of a steroid signaling pathway that regulates the DAF-12 nuclear hormone receptor.
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Affiliation(s)
- Tracy M. Yamawaki
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America
| | - Jennifer R. Berman
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America
| | - Monika Suchanek-Kavipurapu
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America
| | - Mark McCormick
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America
| | - Marta Maria Gaglia
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America
| | - Seung-Jae Lee
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America
| | - Cynthia Kenyon
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail:
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