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Radkohl A, Schusterbauer V, Bernauer L, Rechberger GN, Wolinski H, Schittmayer M, Birner-Gruenberger R, Thallinger GG, Leitner E, Baeck M, Pichler H, Emmerstorfer-Augustin A. Human Sterols Are Overproduced, Stored and Excreted in Yeasts. Int J Mol Sci 2024; 25:781. [PMID: 38255855 PMCID: PMC10815178 DOI: 10.3390/ijms25020781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 12/27/2023] [Accepted: 12/29/2023] [Indexed: 01/24/2024] Open
Abstract
Sterols exert a profound influence on numerous cellular processes, playing a crucial role in both health and disease. However, comprehending the effects of sterol dysfunction on cellular physiology is challenging. Consequently, numerous processes affected by impaired sterol biosynthesis still elude our complete understanding. In this study, we made use of yeast strains that produce cholesterol instead of ergosterol and investigated the cellular response mechanisms on the transcriptome as well as the lipid level. The exchange of ergosterol for cholesterol caused the downregulation of phosphatidylethanolamine and phosphatidylserine and upregulation of phosphatidylinositol and phosphatidylcholine biosynthesis. Additionally, a shift towards polyunsaturated fatty acids was observed. While the sphingolipid levels dropped, the total amounts of sterols and triacylglycerol increased, which resulted in 1.7-fold enlarged lipid droplets in cholesterol-producing yeast cells. In addition to internal storage, cholesterol and its precursors were excreted into the culture supernatant, most likely by the action of ABC transporters Snq2, Pdr12 and Pdr15. Overall, our results demonstrate that, similarly to mammalian cells, the production of non-native sterols and sterol precursors causes lipotoxicity in K. phaffii, mainly due to upregulated sterol biosynthesis, and they highlight the different survival and stress response mechanisms on multiple, integrative levels.
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Affiliation(s)
- Astrid Radkohl
- Institute of Molecular Biotechnology, Graz University of Technology, NAWI Graz, 8010 Graz, Austria
- BioTechMed-Graz, 8010 Graz, Austria
| | - Veronika Schusterbauer
- Bisy GmbH, 8200 Hofstaetten an der Raab, Austria
- Institute of Biomedical Informatics, Graz University of Technology, 8010 Graz, Austria
| | - Lukas Bernauer
- Institute of Molecular Biotechnology, Graz University of Technology, NAWI Graz, 8010 Graz, Austria
- BioTechMed-Graz, 8010 Graz, Austria
| | - Gerald N. Rechberger
- Department of Molecular Biosciences, University of Graz, NAWI Graz, 8010 Graz, Austria
| | - Heimo Wolinski
- Department of Molecular Biosciences, University of Graz, NAWI Graz, 8010 Graz, Austria
- Field of Excellence BioHealth, University of Graz, 8010 Graz, Austria
| | - Matthias Schittmayer
- Institute of Chemical Technologies and Analytics, Technische Universität Wien, 1040 Vienna, Austria (R.B.-G.)
| | - Ruth Birner-Gruenberger
- Institute of Chemical Technologies and Analytics, Technische Universität Wien, 1040 Vienna, Austria (R.B.-G.)
| | - Gerhard G. Thallinger
- Institute of Biomedical Informatics, Graz University of Technology, 8010 Graz, Austria
| | - Erich Leitner
- Institute of Analytical Chemistry and Food Chemistry, University of Graz, NAWI Graz, 8010 Graz, Austria;
| | - Melanie Baeck
- Institute of Molecular Biotechnology, Graz University of Technology, NAWI Graz, 8010 Graz, Austria
| | - Harald Pichler
- Institute of Molecular Biotechnology, Graz University of Technology, NAWI Graz, 8010 Graz, Austria
- BioTechMed-Graz, 8010 Graz, Austria
- Acib—Austrian Centre of Industrial Biotechnology, 8010 Graz, Austria
| | - Anita Emmerstorfer-Augustin
- Institute of Molecular Biotechnology, Graz University of Technology, NAWI Graz, 8010 Graz, Austria
- BioTechMed-Graz, 8010 Graz, Austria
- Acib—Austrian Centre of Industrial Biotechnology, 8010 Graz, Austria
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2
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Jog R, Han GS, Carman GM. The Saccharomyces cerevisiae Spo7 basic tail is required for Nem1-Spo7/Pah1 phosphatase cascade function in lipid synthesis. J Biol Chem 2024; 300:105587. [PMID: 38141768 PMCID: PMC10820825 DOI: 10.1016/j.jbc.2023.105587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 12/04/2023] [Accepted: 12/13/2023] [Indexed: 12/25/2023] Open
Abstract
The Saccharomyces cerevisiae Nem1-Spo7 protein phosphatase complex dephosphorylates and thereby activates Pah1 at the nuclear/endoplasmic reticulum membrane. Pah1, a phosphatidate phosphatase catalyzing the dephosphorylation of phosphatidate to produce diacylglycerol, is one of the most highly regulated enzymes in lipid metabolism. The diacylglycerol produced in the lipid phosphatase reaction is utilized for the synthesis of triacylglycerol that is stored in lipid droplets. Disruptions of the Nem1-Spo7/Pah1 phosphatase cascade cause a plethora of physiological defects. Spo7, the regulatory subunit of the Nem1-Spo7 complex, is required for the Nem1 catalytic function and interacts with the acidic tail of Pah1. Spo7 contains three conserved homology regions (CR1-3) that are important for the interaction with Nem1, but its region for the interaction with Pah1 is unknown. Here, by deletion and site-specific mutational analyses of Spo7, we revealed that the C-terminal basic tail (residues 240-259) containing five arginine and two lysine residues is important for the Nem1-Spo7 complex-mediated dephosphorylation of Pah1 and its cellular function (triacylglycerol synthesis, lipid droplet formation, maintenance of nuclear/endoplasmic reticulum membrane morphology, and cell growth at elevated temperatures). The glutaraldehyde cross-linking analysis of synthetic peptides indicated that the Spo7 basic tail interacts with the Pah1 acidic tail. This work advances our understanding of the Spo7 function and the Nem1-Spo7/Pah1 phosphatase cascade in yeast lipid synthesis.
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Affiliation(s)
- Ruta Jog
- Department of Food Science and the Rutgers Center for Lipid Research, New Jersey Institute for Food, Nutrition, and Health, Rutgers University, New Brunswick, New Jersey, USA
| | - Gil-Soo Han
- Department of Food Science and the Rutgers Center for Lipid Research, New Jersey Institute for Food, Nutrition, and Health, Rutgers University, New Brunswick, New Jersey, USA
| | - George M Carman
- Department of Food Science and the Rutgers Center for Lipid Research, New Jersey Institute for Food, Nutrition, and Health, Rutgers University, New Brunswick, New Jersey, USA.
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3
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Hüsler D, Stauffer P, Hilbi H. Tapping lipid droplets: A rich fat diet of intracellular bacterial pathogens. Mol Microbiol 2023; 120:194-209. [PMID: 37429596 DOI: 10.1111/mmi.15120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 06/21/2023] [Accepted: 06/22/2023] [Indexed: 07/12/2023]
Abstract
Lipid droplets (LDs) are dynamic and versatile organelles present in most eukaryotic cells. LDs consist of a hydrophobic core of neutral lipids, a phospholipid monolayer coat, and a variety of associated proteins. LDs are formed at the endoplasmic reticulum and have diverse roles in lipid storage, energy metabolism, membrane trafficking, and cellular signaling. In addition to their physiological cellular functions, LDs have been implicated in the pathogenesis of several diseases, including metabolic disorders, cancer, and infections. A number of intracellular bacterial pathogens modulate and/or interact with LDs during host cell infection. Members of the genera Mycobacterium, Legionella, Coxiella, Chlamydia, and Salmonella exploit LDs as a source of intracellular nutrients and membrane components to establish their distinct intracellular replicative niches. In this review, we focus on the biogenesis, interactions, and functions of LDs, as well as on their role in lipid metabolism of intracellular bacterial pathogens.
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Affiliation(s)
- Dario Hüsler
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Pia Stauffer
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Hubert Hilbi
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
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4
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Kurokawa Y, Konishi R, Yoshida A, Tomioku K, Tanabe K, Fujita A. Microautophagy in the yeast vacuole depends on the activities of phosphatidylinositol 4-kinases, Stt4p and Pik1p. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183416. [PMID: 32726584 DOI: 10.1016/j.bbamem.2020.183416] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 07/10/2020] [Accepted: 07/12/2020] [Indexed: 12/30/2022]
Abstract
Morphologically, the lipophagy in yeast cell mimics microautophagy, which includes a direct amendment of the vacuolar membrane that engulfs lipid droplets (LDs). The molecular mechanism of the membrane modifications that elicits microautophagy still remains elusive. In this study, an analysis of membrane lipid distribution at a nanoscale level showed that PtdIns(4)P is localized in the cytoplasmic leaflet of microautophagic vesicles, which are derived when the vacuole's membrane domains engulfed LDs both in the stationary phase and in acute nitrogen starvation. Furthermore, the PtdIns(4)P-positive raft-like domains engulf LDs through a microautophagic mechanism. When single temperature-conditional mutants of STT4 or PIK1 PtdIns 4-kinases were used, in the vacuole of STT4 and PIK1 mutant cells, microautophagic vesicles drastically decreased at restrictive temperatures, and the labeling density of PtdIns(4)P on the microautophagic vesicles and the sizes of the mutants' microautophagic vesicles also decreased. These results suggest that both Stt4p and Pik1p have important roles in the microautophagy of the vacuole in the stationary phase and under nitrogen starvation conditions.
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Affiliation(s)
- Yuna Kurokawa
- Department of Molecular and Cell Biology and Biochemistry, Basic Veterinary Science, Faculty of Veterinary Medicine, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan
| | - Rikako Konishi
- Department of Molecular and Cell Biology and Biochemistry, Basic Veterinary Science, Faculty of Veterinary Medicine, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan
| | - Akane Yoshida
- Department of Molecular and Cell Biology and Biochemistry, Basic Veterinary Science, Faculty of Veterinary Medicine, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan
| | - Kanna Tomioku
- Department of Molecular and Cell Biology and Biochemistry, Basic Veterinary Science, Faculty of Veterinary Medicine, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan
| | - Kenji Tanabe
- Medical Research Institute, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan
| | - Akikazu Fujita
- Department of Molecular and Cell Biology and Biochemistry, Basic Veterinary Science, Faculty of Veterinary Medicine, Kagoshima University, Korimoto 1-21-24, Kagoshima 890-0065, Japan.
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5
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Csáky Z, Garaiová M, Kodedová M, Valachovič M, Sychrová H, Hapala I. Squalene lipotoxicity in a lipid droplet‐less yeast mutant is linked to plasma membrane dysfunction. Yeast 2020; 37:45-62. [DOI: 10.1002/yea.3454] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 12/02/2019] [Accepted: 12/07/2019] [Indexed: 12/13/2022] Open
Affiliation(s)
- Zsófia Csáky
- Department of Membrane Biochemistry Institute of Animal Biochemistry and Genetics, Centre of Biosciences of the Slovak Academy of Sciences Bratislava Slovakia
| | - Martina Garaiová
- Department of Membrane Biochemistry Institute of Animal Biochemistry and Genetics, Centre of Biosciences of the Slovak Academy of Sciences Bratislava Slovakia
| | - Marie Kodedová
- Department of Membrane Transport, Division BIOCEV Institute of Physiology of the Czech Academy of Sciences Prague Czech Republic
| | - Martin Valachovič
- Department of Membrane Biochemistry Institute of Animal Biochemistry and Genetics, Centre of Biosciences of the Slovak Academy of Sciences Bratislava Slovakia
| | - Hana Sychrová
- Department of Membrane Transport, Division BIOCEV Institute of Physiology of the Czech Academy of Sciences Prague Czech Republic
| | - Ivan Hapala
- Department of Membrane Biochemistry Institute of Animal Biochemistry and Genetics, Centre of Biosciences of the Slovak Academy of Sciences Bratislava Slovakia
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6
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Medkour Y, Mohammad K, Arlia-Ciommo A, Svistkova V, Dakik P, Mitrofanova D, Rodriguez MEL, Junio JAB, Taifour T, Escudero P, Goltsios FF, Soodbakhsh S, Maalaoui H, Simard É, Titorenko VI. Mechanisms by which PE21, an extract from the white willow Salix alba, delays chronological aging in budding yeast. Oncotarget 2019; 10:5780-5816. [PMID: 31645900 PMCID: PMC6791382 DOI: 10.18632/oncotarget.27209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 08/27/2019] [Indexed: 01/05/2023] Open
Abstract
We have recently found that PE21, an extract from the white willow Salix alba, slows chronological aging and prolongs longevity of the yeast Saccharomyces cerevisiae more efficiently than any of the previously known pharmacological interventions. Here, we investigated mechanisms through which PE21 delays yeast chronological aging and extends yeast longevity. We show that PE21 causes a remodeling of lipid metabolism in chronologically aging yeast, thereby instigating changes in the concentrations of several lipid classes. We demonstrate that such changes in the cellular lipidome initiate three mechanisms of aging delay and longevity extension. The first mechanism through which PE21 slows aging and prolongs longevity consists in its ability to decrease the intracellular concentration of free fatty acids. This postpones an age-related onset of liponecrotic cell death promoted by excessive concentrations of free fatty acids. The second mechanism of aging delay and longevity extension by PE21 consists in its ability to decrease the concentrations of triacylglycerols and to increase the concentrations of glycerophospholipids within the endoplasmic reticulum membrane. This activates the unfolded protein response system in the endoplasmic reticulum, which then decelerates an age-related decline in protein and lipid homeostasis and slows down an aging-associated deterioration of cell resistance to stress. The third mechanisms underlying aging delay and longevity extension by PE21 consists in its ability to change lipid concentrations in the mitochondrial membranes. This alters certain catabolic and anabolic processes in mitochondria, thus amending the pattern of aging-associated changes in several key aspects of mitochondrial functionality.
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Affiliation(s)
- Younes Medkour
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Karamat Mohammad
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | | | - Veronika Svistkova
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Pamela Dakik
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Darya Mitrofanova
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | | | | | - Tarek Taifour
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Paola Escudero
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Fani-Fay Goltsios
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Sahar Soodbakhsh
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Hana Maalaoui
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Éric Simard
- Idunn Technologies Inc., Rosemere, Quebec J7A 4A5, Canada
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7
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Quantitative Mapping of Triacylglycerol Chain Length and Saturation Using Broadband CARS Microscopy. Biophys J 2019; 116:2346-2355. [PMID: 31153590 DOI: 10.1016/j.bpj.2019.04.036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 03/25/2019] [Accepted: 04/25/2019] [Indexed: 01/15/2023] Open
Abstract
Lipid droplets (LDs), present in many cell types, are highly dynamic organelles that store neutral lipids, primarily triacylglycerols (TAGs). With the discovery of new LD functions (e.g., in immune response, protein clearage, and occurrence with disease), new methods to study LD chemical composition in situ are necessary. We present an approach for in situ, quantitative TAG analysis using label-free, coherent Raman microscopy that allows deciphering LD TAG composition in different biochemically complex samples with submicrometer spatial resolution. Employing a set of standard TAGs, we generate a spectral training matrix capturing the variation caused in Raman-like spectra by TAG backbone, chain length, and number of double bonds per chain, as well as the presence of proteins or other diluting molecules. Comparing our fitting approach to gas chromatography measurements for mixtures of standard TAGs and food oils, we find the root mean-square error for the prediction of TAG chemistry to be 0.69 CH2 and 0.15 #C=C. When progressing to more complex samples such as oil emulsions and LDs in various eukaryotic cells, we find good agreement with bulk gas chromatography measurements. For differentiated adipocytes, we find a significant increase in the number of double bonds in small LDs (below 2 μm in diameter) compared to large LDs (above 2 μm in diameter). Coupled with a relatively limited sample preparation requirement, this approach should enable rapid and accurate TAG LD analysis for a variety of cell biology and technological applications.
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8
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Ganesan S, Sosa Ponce ML, Tavassoli M, Shabits BN, Mahadeo M, Prenner EJ, Terebiznik MR, Zaremberg V. Metabolic control of cytosolic-facing pools of diacylglycerol in budding yeast. Traffic 2019; 20:226-245. [PMID: 30569465 DOI: 10.1111/tra.12632] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 12/18/2018] [Accepted: 12/18/2018] [Indexed: 12/12/2022]
Abstract
Diacylglycerol (DAG) is a key signaling lipid and intermediate in lipid metabolism. Our knowledge of DAG distribution and dynamics in cell membranes is limited. Using live-cell fluorescence microscopy we investigated the localization of yeast cytosolic-facing pools of DAG in response to conditions where lipid homeostasis and DAG levels were known to be altered. Two main pools were monitored over time using DAG sensors. One pool was associated with vacuolar membranes and the other localized to sites of polarized growth. Dynamic changes in DAG distribution were observed during resumption of growth from stationary phase, when DAG is used to support phospholipid synthesis for membrane proliferation. Vacuolar membranes experienced constant morphological changes displaying DAG enriched microdomains coexisting with liquid-disordered areas demarcated by Vph1. Formation of these domains was dependent on triacylglycerol (TAG) lipolysis. DAG domains and puncta were closely connected to lipid droplets. Lack of conversion of DAG to phosphatidate in growth conditions dependent on TAG mobilization, led to the accumulation of DAG in a vacuolar-associated compartment, impacting the polarized distribution of DAG at budding sites. DAG polarization was also regulated by phosphatidylserine synthesis/traffic and sphingolipid synthesis in the Golgi.
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Affiliation(s)
| | - Maria L Sosa Ponce
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Marjan Tavassoli
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Brittney N Shabits
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Mark Mahadeo
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Elmar J Prenner
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Mauricio R Terebiznik
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada.,Department of Cell and System Biology, University of Toronto Scarborough, Toronto, Ontario, Canada
| | - Vanina Zaremberg
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
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9
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Astragalosides IV protected the renal tubular epithelial cells from free fatty acids-induced injury by reducing oxidative stress and apoptosis. Biomed Pharmacother 2018; 108:679-686. [DOI: 10.1016/j.biopha.2018.09.049] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Revised: 09/08/2018] [Accepted: 09/08/2018] [Indexed: 01/17/2023] Open
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10
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Yeast Cells Exposed to Exogenous Palmitoleic Acid Either Adapt to Stress and Survive or Commit to Regulated Liponecrosis and Die. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:3074769. [PMID: 29636840 PMCID: PMC5831759 DOI: 10.1155/2018/3074769] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2017] [Revised: 11/27/2017] [Accepted: 12/20/2017] [Indexed: 12/11/2022]
Abstract
A disturbed homeostasis of cellular lipids and the resulting lipotoxicity are considered to be key contributors to many human pathologies, including obesity, metabolic syndrome, type 2 diabetes, cardiovascular diseases, and cancer. The yeast Saccharomyces cerevisiae has been successfully used for uncovering molecular mechanisms through which impaired lipid metabolism causes lipotoxicity and elicits different forms of regulated cell death. Here, we discuss mechanisms of the “liponecrotic” mode of regulated cell death in S. cerevisiae. This mode of regulated cell death can be initiated in response to a brief treatment of yeast with exogenous palmitoleic acid. Such treatment prompts the incorporation of exogenously added palmitoleic acid into phospholipids and neutral lipids. This orchestrates a global remodeling of lipid metabolism and transfer in the endoplasmic reticulum, mitochondria, lipid droplets, and the plasma membrane. Certain features of such remodeling play essential roles either in committing yeast to liponecrosis or in executing this mode of regulated cell death. We also outline four processes through which yeast cells actively resist liponecrosis by adapting to the cellular stress imposed by palmitoleic acid and maintaining viability. These prosurvival cellular processes are confined in the endoplasmic reticulum, lipid droplets, peroxisomes, autophagosomes, vacuoles, and the cytosol.
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11
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Renne MF, de Kroon AIPM. The role of phospholipid molecular species in determining the physical properties of yeast membranes. FEBS Lett 2017; 592:1330-1345. [PMID: 29265372 PMCID: PMC5947837 DOI: 10.1002/1873-3468.12944] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 11/27/2017] [Accepted: 12/11/2017] [Indexed: 12/18/2022]
Abstract
In most eukaryotes, including Saccharomyces cerevisiae, glycerophospholipids are the main membrane lipid constituents. Besides serving as general membrane ‘building blocks’, glycerophospholipids play an important role in determining the physical properties of the membrane, which are crucial for proper membrane function. To ensure optimal physical properties, membrane glycerophospholipid composition and synthesis are tightly regulated. This review will summarize our current knowledge of factors and processes determining the membrane glycerophospholipid composition of the reference eukaryote S. cerevisiae at the level of molecular species. Extrapolating from relevant model membrane data, we also discuss how modulation of the molecular species composition can regulate membrane physical properties.
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Affiliation(s)
- Mike F. Renne
- Membrane Biochemistry & BiophysicsDepartment of ChemistryBijvoet Center for Biomolecular Research & Institute of BiomembranesUtrecht Universitythe Netherlands
| | - Anton I. P. M. de Kroon
- Membrane Biochemistry & BiophysicsDepartment of ChemistryBijvoet Center for Biomolecular Research & Institute of BiomembranesUtrecht Universitythe Netherlands
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12
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Hayes M, Choudhary V, Ojha N, Shin JJ, Han GS, Carman GM, Loewen CJ, Prinz WA, Levine T. Fat storage-inducing transmembrane (FIT or FITM) proteins are related to lipid phosphatase/phosphotransferase enzymes. ACTA ACUST UNITED AC 2017; 5:88-103. [PMID: 29417057 PMCID: PMC5798408 DOI: 10.15698/mic2018.02.614] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Fat storage-inducing transmembrane (FIT or FITM) proteins have been implicated in the partitioning of triacylglycerol to lipid droplets and the budding of lipid droplets from the ER. At the molecular level, the sole relevant interaction is that FITMs directly bind to triacyglycerol and diacylglycerol, but how they function at the molecular level is not known. Saccharomyces cerevisiae has two FITM homologues: Scs3p and Yft2p. Scs3p was initially identified because deletion leads to inositol auxotrophy, with an unusual sensitivity to addition of choline. This strongly suggests a role for Scs3p in phospholipid biosynthesis. Looking at the FITM family as widely as possible, we found that FITMs are widespread throughout eukaryotes, indicating presence in the last eukaryotic common ancestor. Protein alignments also showed that FITM sequences contain the active site of lipid phosphatase/phosphotransferase (LPT) enzymes. This large family transfers phosphate-containing headgroups either between lipids or in exchange for water. We confirmed the prediction that FITMs are related to LPTs by showing that single amino-acid substitutions in the presumptive catalytic site prevented their ability to rescue growth of the mutants on low inositol/high choline media when over-expressed. The substitutions also prevented rescue of other phenotypes associated with loss of FITM in yeast, including mistargeting of Opi1p, defective ER morphology, and aberrant lipid droplet budding. These results suggest that Scs3p, Yft2p and FITMs in general are LPT enzymes involved in an as yet unknown critical step in phospholipid metabolism.
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Affiliation(s)
- Matthew Hayes
- University College London Institute of Ophthalmology. 11-43 Bath Street, London, EC1V 9EL, UK
| | - Vineet Choudhary
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Namrata Ojha
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - John Jh Shin
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Gil-Soo Han
- Department of Food Science and Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901, USA
| | - George M Carman
- Department of Food Science and Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901, USA
| | - Christopher Jr Loewen
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - William A Prinz
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Timothy Levine
- University College London Institute of Ophthalmology. 11-43 Bath Street, London, EC1V 9EL, UK
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13
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Rajakumar T, Munkacsi AB, Sturley SL. Exacerbating and reversing lysosomal storage diseases: from yeast to humans. MICROBIAL CELL 2017; 4:278-293. [PMID: 28913343 PMCID: PMC5597791 DOI: 10.15698/mic2017.09.588] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Lysosomal storage diseases (LSDs) arise from monogenic deficiencies in lysosomal proteins and pathways and are characterized by a tissue-wide accumulation of a vast variety of macromolecules, normally specific to each genetic lesion. Strategies for treatment of LSDs commonly depend on reduction of the offending metabolite(s) by substrate depletion or enzyme replacement. However, at least 44 of the ~50 LSDs are currently recalcitrant to intervention. Murine models have provided significant insights into our understanding of many LSD mechanisms; however, these systems do not readily permit phenotypic screening of compound libraries, or the establishment of genetic or gene-environment interaction networks. Many of the genes causing LSDs are evolutionarily conserved, thus facilitating the application of models system to provide additional insight into LSDs. Here, we review the utility of yeast models of 3 LSDs: Batten disease, cystinosis, and Niemann-Pick type C disease. We will focus on the translation of research from yeast models into human patients suffering from these LSDs. We will also discuss the use of yeast models to investigate the penetrance of LSDs, such as Niemann-Pick type C disease, into more prevalent syndromes including viral infection and obesity.
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Affiliation(s)
- Tamayanthi Rajakumar
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand 6012
| | - Andrew B Munkacsi
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand 6012.,Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand 6012
| | - Stephen L Sturley
- Department of Genetics and Development, Columbia University Medical Center, New York, NY 10032
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14
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Lipid droplet growth and adipocyte development: mechanistically distinct processes connected by phospholipids. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1273-1283. [PMID: 28668300 DOI: 10.1016/j.bbalip.2017.06.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Revised: 06/20/2017] [Accepted: 06/23/2017] [Indexed: 12/19/2022]
Abstract
The differentiation of preadipocytes into mature adipocytes is accompanied by the growth and formation of a giant, unilocular lipid droplet (LD). Mechanistically however, LD growth and adipogenesis are two different processes. Recent studies have uncovered a number of proteins that are able to regulate both LD dynamics and adipogenesis, such as SEIPIN, LIPIN and CDP-Diacylglycerol Synthases. It appears that phospholipids, phosphatidic acid in particular, play a critical role in both LD budding/growth and adipocyte development. This review summarizes recent advances, and aims to provide a better understanding of LD growth as well as adipogenesis, two critical aspects in mammalian fat storage. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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15
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Hokkanen S, Laakso S, Senn CM, Frey AD. The trans-10,cis-12 conjugated linoleic acid increases triacylglycerol hydrolysis in yeast Saccharomyces cerevisiae. J Appl Microbiol 2017; 123:185-193. [PMID: 28276610 DOI: 10.1111/jam.13443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Revised: 01/13/2017] [Accepted: 03/02/2017] [Indexed: 11/29/2022]
Abstract
AIMS The trans-10,cis-12 conjugated linoleic acid (CLA) is known for its antilipogenic effect but the mechanism is not fully clear. In this study, the potential of yeast (Saccharomyces cerevisiae) metabolism to offer evidence for the mechanism was investigated. METHODS AND RESULTS The inhibitory effect of CLA on lipid accumulation was studied by analysing the transcript abundance of selected genes involved in triacylglycerol synthesis (LRO1, DGA1, ARE1 and ARE2) in the presence of the two bioactive CLA isomers: trans-10,cis-12 and the cis-9,trans-11 CLA. None of the enzymes was reduced in transcription but the expression of ARE2 was induced by trans-10,cis-12 CLA. However, the ARE2 overexpression did not contribute to lipid accumulation. The expression of the Δ9 desaturase gene, OLE1, was reduced by the cis-9,trans-11 but not by the trans-10,cis-12 isomer. In the TGL3/TGL4-knockout strain the triacylglycerol content also remained high in the CLA fed cells. CONCLUSIONS Triacylglycerol hydrolysis rather than synthesis was the most probable reason for the reduced lipid content in yeast induced by CLA. SIGNIFICANCE AND IMPACT OF THE STUDY This study revealed new aspects of the functionality of CLA in eukaryotic lipid metabolism. Yeast was proven to be an applicable model to study further the mechanism of trans-10,cis-12 CLA functionality on lipid metabolism.
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Affiliation(s)
- S Hokkanen
- Department of Bioproducts and Biosystems, Aalto University, Espoo, Finland
| | - S Laakso
- Department of Bioproducts and Biosystems, Aalto University, Espoo, Finland
| | - C M Senn
- Laves-Arzneimittel GmbH, Schötz, Switzerland
| | - A D Frey
- Department of Bioproducts and Biosystems, Aalto University, Espoo, Finland
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16
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Wang S, Peng J. Network-assisted target identification for haploinsufficiency and homozygous profiling screens. PLoS Comput Biol 2017; 13:e1005553. [PMID: 28574983 PMCID: PMC5482495 DOI: 10.1371/journal.pcbi.1005553] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Revised: 06/23/2017] [Accepted: 05/05/2017] [Indexed: 12/20/2022] Open
Abstract
Chemical genomic screens have recently emerged as a systematic approach to drug discovery on a genome-wide scale. Drug target identification and elucidation of the mechanism of action (MoA) of hits from these noisy high-throughput screens remain difficult. Here, we present GIT (Genetic Interaction Network-Assisted Target Identification), a network analysis method for drug target identification in haploinsufficiency profiling (HIP) and homozygous profiling (HOP) screens. With the drug-induced phenotypic fitness defect of the deletion of a gene, GIT also incorporates the fitness defects of the gene's neighbors in the genetic interaction network. On three genome-scale yeast chemical genomic screens, GIT substantially outperforms previous scoring methods on target identification on HIP and HOP assays, respectively. Finally, we showed that by combining HIP and HOP assays, GIT further boosts target identification and reveals potential drug's mechanism of action.
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Affiliation(s)
- Sheng Wang
- Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Jian Peng
- Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
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17
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Valachovic M, Garaiova M, Holic R, Hapala I. Squalene is lipotoxic to yeast cells defective in lipid droplet biogenesis. Biochem Biophys Res Commun 2015; 469:1123-8. [PMID: 26703208 DOI: 10.1016/j.bbrc.2015.12.050] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 12/13/2015] [Indexed: 12/01/2022]
Abstract
The toxic effect of overloaded lipids on cell physiology and viability was described in various organisms. In this study we focused on the potential lipotoxicity of squalene, a linear triterpene synthesized in eukaryotic cells as an intermediate in sterol biosynthesis. Squalene toxicity was studied in the yeast Saccharomyces cerevisiae, a model unicellular eukaryote established in lipotoxicity studies. Squalene levels in yeast are typically low but its accumulation can be induced under specific conditions, e.g. by inhibition of squalene monooxygenase with the antimycotic terbinafine. At higher levels squalene is stored in lipid droplets. We demonstrated that low doses of terbinafine caused severe impairment of growth and loss of viability of the yeast mutant dga1Δ lro1Δ are1Δ are2Δ unable to form lipid droplets and that these defects were linked to squalene accumulation. The hypersensitivity of the lipid droplet-less mutant to terbinafine was alleviated by decreasing squalene accumulation with low doses of squalene synthase inhibitor zaragozic acid. Our results proved that accumulated squalene is lipotoxic to yeast cells if it cannot be efficiently sequestered in lipid droplets. This supports the hypothesis about the role of squalene in the fungicidal activity of terbinafine. Squalene toxicity may represent also a limiting factor for production of this high-value lipid in yeast.
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Affiliation(s)
- Martin Valachovic
- Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Moyzesova 61, 90028 Ivanka pri Dunaji, Slovak Republic
| | - Martina Garaiova
- Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Moyzesova 61, 90028 Ivanka pri Dunaji, Slovak Republic
| | - Roman Holic
- Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Moyzesova 61, 90028 Ivanka pri Dunaji, Slovak Republic
| | - Ivan Hapala
- Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Moyzesova 61, 90028 Ivanka pri Dunaji, Slovak Republic.
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18
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Experimental and computational analysis of a large protein network that controls fat storage reveals the design principles of a signaling network. PLoS Comput Biol 2015; 11:e1004264. [PMID: 26020510 PMCID: PMC4447291 DOI: 10.1371/journal.pcbi.1004264] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 04/02/2015] [Indexed: 01/26/2023] Open
Abstract
An approach combining genetic, proteomic, computational, and physiological analysis was used to define a protein network that regulates fat storage in budding yeast (Saccharomyces cerevisiae). A computational analysis of this network shows that it is not scale-free, and is best approximated by the Watts-Strogatz model, which generates “small-world” networks with high clustering and short path lengths. The network is also modular, containing energy level sensing proteins that connect to four output processes: autophagy, fatty acid synthesis, mRNA processing, and MAP kinase signaling. The importance of each protein to network function is dependent on its Katz centrality score, which is related both to the protein’s position within a module and to the module’s relationship to the network as a whole. The network is also divisible into subnetworks that span modular boundaries and regulate different aspects of fat metabolism. We used a combination of genetics and pharmacology to simultaneously block output from multiple network nodes. The phenotypic results of this blockage define patterns of communication among distant network nodes, and these patterns are consistent with the Watts-Strogatz model. We discovered a large protein network that regulates fat storage in budding yeast. This network contains 94 proteins, almost all of which bind to other proteins in the network. To understand the functions of large protein collections such as these, it will be necessary to move away from one-by-one analysis of individual proteins and create computational models of entire networks. This will allow classification of networks into categories and permit researchers to identify key network proteins on theoretical grounds. We show here that the fat regulation network fits a Watts-Strogatz small-world model. This model was devised to explain the clustering phenomena often observed in real networks, but has not been previously applied to signaling networks within cells. The short path length and high clustering coefficients characteristic of the Watts-Strogatz topology allow for rapid communication between distant nodes and for division of the network into modules that perform different functions. The fat regulation network has modules, and it is divisible into subnetworks that span modular boundaries and regulate different aspects of fat metabolism. We experimentally examined communication between nodes within the network using a combination of genetics and pharmacology, and showed that the communication patterns are consistent with the Watts-Strogatz topology.
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19
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Baker’s Yeast Deficient in Storage Lipid Synthesis Uses cis-Vaccenic Acid to Reduce Unsaturated Fatty Acid Toxicity. Lipids 2015; 50:621-30. [DOI: 10.1007/s11745-015-4022-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 04/08/2015] [Indexed: 01/22/2023]
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20
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Hashemi HF, Goodman JM. The life cycle of lipid droplets. Curr Opin Cell Biol 2015; 33:119-24. [PMID: 25703629 DOI: 10.1016/j.ceb.2015.02.002] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 01/28/2015] [Accepted: 02/02/2015] [Indexed: 01/14/2023]
Abstract
Proteomic studies have revealed many potential functions of cytoplasmic lipid droplets, and recent activity has confirmed that these bona fide organelles are central not only for lipid storage and metabolism, but for development, immunity, and pathogenesis by several microbes. There has been a burst of recent activity on the assembly, maintenance and turnover of lipid droplets that reveals fresh insights. This review summarizes several novel findings in initiation of lipid droplet assembly, protein targeting, droplet fusion, and turnover of droplets through lipophagy.
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Affiliation(s)
- Hayaa F Hashemi
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, United States
| | - Joel M Goodman
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9041, United States.
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21
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Transcriptional and antioxidative responses to endogenous polyunsaturated fatty acid accumulation in yeast. Mol Cell Biochem 2014; 399:27-37. [PMID: 25280400 DOI: 10.1007/s11010-014-2229-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 09/27/2014] [Indexed: 01/06/2023]
Abstract
Pathophysiology of polyunsaturated fatty acids (PUFAs) is associated with aberrant lipid and oxygen metabolism. In particular, under oxidative stress, PUFAs are prone to autocatalytic degradation via peroxidation, leading to formation of reactive aldehydes with numerous potentially harmful effects. However, the pathological and compensatory mechanisms induced by lipid peroxidation are very complex and not sufficiently understood. In our study, we have used yeast capable of endogenous PUFA synthesis in order to understand the effects triggered by PUFA accumulation on cellular physiology of a eukaryotic organism. The mechanisms induced by PUFA accumulation in S. cerevisiae expressing Hevea brasiliensis Δ12-fatty acid desaturase include down-regulation of components of electron transport chain in mitochondria as well as up-regulation of pentose-phosphate pathway and fatty acid β-oxidation at the transcriptional level. Interestingly, while no changes were observed at the transcriptional level, activities of two important enzymatic antioxidants, catalase and glutathione-S-transferase, were altered in response to PUFA accumulation. Increased intracellular glutathione levels further suggest an endogenous oxidative stress and activation of antioxidative defense mechanisms under conditions of PUFA accumulation. Finally, our data suggest that PUFA in cell membrane causes metabolic changes which in turn lead to adaptation to endogenous oxidative stress.
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22
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Hofbauer HF, Schopf FH, Schleifer H, Knittelfelder OL, Pieber B, Rechberger GN, Wolinski H, Gaspar ML, Kappe CO, Stadlmann J, Mechtler K, Zenz A, Lohner K, Tehlivets O, Henry SA, Kohlwein SD. Regulation of gene expression through a transcriptional repressor that senses acyl-chain length in membrane phospholipids. Dev Cell 2014; 29:729-39. [PMID: 24960695 PMCID: PMC4070385 DOI: 10.1016/j.devcel.2014.04.025] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 04/01/2014] [Accepted: 04/22/2014] [Indexed: 12/20/2022]
Abstract
Membrane phospholipids typically contain fatty acids (FAs) of 16 and 18 carbon atoms. This particular chain length is evolutionarily highly conserved and presumably provides maximum stability and dynamic properties to biological membranes in response to nutritional or environmental cues. Here, we show that the relative proportion of C16 versus C18 FAs is regulated by the activity of acetyl-CoA carboxylase (Acc1), the first and rate-limiting enzyme of FA de novo synthesis. Acc1 activity is attenuated by AMPK/Snf1-dependent phosphorylation, which is required to maintain an appropriate acyl-chain length distribution. Moreover, we find that the transcriptional repressor Opi1 preferentially binds to C16 over C18 phosphatidic acid (PA) species: thus, C16-chain containing PA sequesters Opi1 more effectively to the ER, enabling AMPK/Snf1 control of PA acyl-chain length to determine the degree of derepression of Opi1 target genes. These findings reveal an unexpected regulatory link between the major energy-sensing kinase, membrane lipid composition, and transcription. AMPK/Snf1 inhibition of acetyl-CoA carboxylase controls fatty acyl-chain length Opi1 repressor preferentially binds to C16 rather than C18 acyl-chains in PA Acyl-chain length tunes Opi1 sequestration to the ER and target gene derepression AMPK/Snf1 thus uses its effect on acyl-chain length to control Opi1 target genes
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Affiliation(s)
- Harald F Hofbauer
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria
| | - Florian H Schopf
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria
| | - Hannes Schleifer
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria
| | - Oskar L Knittelfelder
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria
| | - Bartholomäus Pieber
- Institute of Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - Gerald N Rechberger
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria
| | - Heimo Wolinski
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria
| | - Maria L Gaspar
- Department of Molecular Biology and Genetics, 249 Biotechnology Building, Cornell University, Ithaca, NY 14853-2703, USA
| | - C Oliver Kappe
- Institute of Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - Johannes Stadlmann
- Protein Chemistry Facility, Institute of Molecular Pathology (IMP), Doktor-Bohr-Gasse 7, 1030 Vienna, Austria
| | - Karl Mechtler
- Protein Chemistry Facility, IMBA Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Doktor-Bohr-Gasse 3, 1030 Vienna, Austria
| | - Alexandra Zenz
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria
| | - Karl Lohner
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria
| | - Oksana Tehlivets
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria
| | - Susan A Henry
- Department of Molecular Biology and Genetics, 249 Biotechnology Building, Cornell University, Ithaca, NY 14853-2703, USA
| | - Sepp D Kohlwein
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/II, 8010 Graz, Austria; BioTechMed Graz, 8010 Graz, Austria.
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23
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van Zutphen T, Todde V, de Boer R, Kreim M, Hofbauer HF, Wolinski H, Veenhuis M, van der Klei IJ, Kohlwein SD. Lipid droplet autophagy in the yeast Saccharomyces cerevisiae. Mol Biol Cell 2013; 25:290-301. [PMID: 24258026 PMCID: PMC3890349 DOI: 10.1091/mbc.e13-08-0448] [Citation(s) in RCA: 219] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cytosolic lipid droplets (LDs) are ubiquitous organelles in prokaryotes and eukaryotes that play a key role in cellular and organismal lipid homeostasis. Triacylglycerols (TAGs) and steryl esters, which are stored in LDs, are typically mobilized in growing cells or upon hormonal stimulation by LD-associated lipases and steryl ester hydrolases. Here we show that in the yeast Saccharomyces cerevisiae, LDs can also be turned over in vacuoles/lysosomes by a process that morphologically resembles microautophagy. A distinct set of proteins involved in LD autophagy is identified, which includes the core autophagic machinery but not Atg11 or Atg20. Thus LD autophagy is distinct from endoplasmic reticulum-autophagy, pexophagy, or mitophagy, despite the close association between these organelles. Atg15 is responsible for TAG breakdown in vacuoles and is required to support growth when de novo fatty acid synthesis is compromised. Furthermore, none of the core autophagy proteins, including Atg1 and Atg8, is required for LD formation in yeast.
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Affiliation(s)
- Tim van Zutphen
- Molecular Cell Biology, University of Groningen, 9747 AG Groningen, Netherlands Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
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24
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Eisenberg T, Büttner S. Lipids and cell death in yeast. FEMS Yeast Res 2013; 14:179-97. [PMID: 24119111 PMCID: PMC4255311 DOI: 10.1111/1567-1364.12105] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 08/21/2013] [Accepted: 09/25/2013] [Indexed: 01/22/2023] Open
Abstract
Understanding lipid-induced malfunction represents a major challenge of today's biomedical research. The connection of lipids to cellular and organ dysfunction, cell death, and disease (often referred to as lipotoxicity) is more complex than the sole lipotoxic effects of excess free fatty acids and requires genetically tractable model systems for mechanistic investigation. We herein summarize recent advances in the field of lipid-induced toxicity that employ the established model system for cell death and aging research of budding yeast Saccharomyces cerevisiae. Studies in yeast have shed light on various aspects of lipotoxicity, including free fatty acid toxicity, sphingolipid-modulated cell death as well as the involvement of cardiolipin and lipid peroxidation in the mitochondrial pathways of apoptosis. Regimens used range from exogenously applied lipids, genetic modulation of lipolysis and triacylglyceride synthesis, variations in sphingolipid/ceramide metabolism as well as changes in peroxisome function by either genetic or pharmacological means. In future, the yeast model of programmed cell death will further contribute to the clarification of crucial questions of lipid-associated malfunction.
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Affiliation(s)
- Tobias Eisenberg
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
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25
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Secretory production of ricinoleic acid in fission yeast Schizosaccharomyces pombe. Appl Microbiol Biotechnol 2013; 97:8663-71. [DOI: 10.1007/s00253-013-5060-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 06/11/2013] [Accepted: 06/13/2013] [Indexed: 10/26/2022]
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26
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Lipid droplets and peroxisomes: key players in cellular lipid homeostasis or a matter of fat--store 'em up or burn 'em down. Genetics 2013; 193:1-50. [PMID: 23275493 PMCID: PMC3527239 DOI: 10.1534/genetics.112.143362] [Citation(s) in RCA: 166] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Lipid droplets (LDs) and peroxisomes are central players in cellular lipid homeostasis: some of their main functions are to control the metabolic flux and availability of fatty acids (LDs and peroxisomes) as well as of sterols (LDs). Both fatty acids and sterols serve multiple functions in the cell—as membrane stabilizers affecting membrane fluidity, as crucial structural elements of membrane-forming phospholipids and sphingolipids, as protein modifiers and signaling molecules, and last but not least, as a rich carbon and energy source. In addition, peroxisomes harbor enzymes of the malic acid shunt, which is indispensable to regenerate oxaloacetate for gluconeogenesis, thus allowing yeast cells to generate sugars from fatty acids or nonfermentable carbon sources. Therefore, failure of LD and peroxisome biogenesis and function are likely to lead to deregulated lipid fluxes and disrupted energy homeostasis with detrimental consequences for the cell. These pathological consequences of LD and peroxisome failure have indeed sparked great biomedical interest in understanding the biogenesis of these organelles, their functional roles in lipid homeostasis, interaction with cellular metabolism and other organelles, as well as their regulation, turnover, and inheritance. These questions are particularly burning in view of the pandemic development of lipid-associated disorders worldwide.
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27
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Yazawa H, Holic R, Kumagai H, Uemura H. Toxicity of ricinoleic acid production in fission yeast Schizosaccharomyces pombe is suppressed by the overexpression of plg7, a phospholipase A2 of a platelet-activating factor (PAF) family homolog. Appl Microbiol Biotechnol 2013; 97:8193-203. [DOI: 10.1007/s00253-013-4987-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 05/06/2013] [Accepted: 05/07/2013] [Indexed: 12/01/2022]
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Tehlivets O, Malanovic N, Visram M, Pavkov-Keller T, Keller W. S-adenosyl-L-homocysteine hydrolase and methylation disorders: yeast as a model system. Biochim Biophys Acta Mol Basis Dis 2012; 1832:204-15. [PMID: 23017368 PMCID: PMC3787734 DOI: 10.1016/j.bbadis.2012.09.007] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 09/14/2012] [Accepted: 09/18/2012] [Indexed: 12/14/2022]
Abstract
S-adenosyl-L-methionine (AdoMet)-dependent methylation is central to the regulation of many biological processes: more than 50 AdoMet-dependent methyltransferases methylate a broad spectrum of cellular compounds including nucleic acids, proteins and lipids. Common to all AdoMet-dependent methyltransferase reactions is the release of the strong product inhibitor S-adenosyl-L-homocysteine (AdoHcy), as a by-product of the reaction. S-adenosyl-L-homocysteine hydrolase is the only eukaryotic enzyme capable of reversible AdoHcy hydrolysis to adenosine and homocysteine and, thus, relief from AdoHcy inhibition. Impaired S-adenosyl-L-homocysteine hydrolase activity in humans results in AdoHcy accumulation and severe pathological consequences. Hyperhomocysteinemia, which is characterized by elevated levels of homocysteine in blood, also exhibits a similar phenotype of AdoHcy accumulation due to the reversal of the direction of the S-adenosyl-L-homocysteine hydrolase reaction. Inhibition of S-adenosyl-L-homocysteine hydrolase is also linked to antiviral effects. In this review the advantages of yeast as an experimental system to understand pathologies associated with AdoHcy accumulation will be discussed.
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Affiliation(s)
- Oksana Tehlivets
- Institute of Molecular Biosciences, University of Graz, Graz, Austria.
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Abstract
Due to its genetic tractability and increasing wealth of accessible data, the yeast Saccharomyces cerevisiae is a model system of choice for the study of the genetics, biochemistry, and cell biology of eukaryotic lipid metabolism. Glycerolipids (e.g., phospholipids and triacylglycerol) and their precursors are synthesized and metabolized by enzymes associated with the cytosol and membranous organelles, including endoplasmic reticulum, mitochondria, and lipid droplets. Genetic and biochemical analyses have revealed that glycerolipids play important roles in cell signaling, membrane trafficking, and anchoring of membrane proteins in addition to membrane structure. The expression of glycerolipid enzymes is controlled by a variety of conditions including growth stage and nutrient availability. Much of this regulation occurs at the transcriptional level and involves the Ino2–Ino4 activation complex and the Opi1 repressor, which interacts with Ino2 to attenuate transcriptional activation of UASINO-containing glycerolipid biosynthetic genes. Cellular levels of phosphatidic acid, precursor to all membrane phospholipids and the storage lipid triacylglycerol, regulates transcription of UASINO-containing genes by tethering Opi1 to the nuclear/endoplasmic reticulum membrane and controlling its translocation into the nucleus, a mechanism largely controlled by inositol availability. The transcriptional activator Zap1 controls the expression of some phospholipid synthesis genes in response to zinc availability. Regulatory mechanisms also include control of catalytic activity of glycerolipid enzymes by water-soluble precursors, products and lipids, and covalent modification of phosphorylation, while in vivo function of some enzymes is governed by their subcellular location. Genome-wide genetic analysis indicates coordinate regulation between glycerolipid metabolism and a broad spectrum of metabolic pathways.
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Homocysteine as a risk factor for atherosclerosis: is its conversion to s-adenosyl-L-homocysteine the key to deregulated lipid metabolism? J Lipids 2011; 2011:702853. [PMID: 21837278 PMCID: PMC3151505 DOI: 10.1155/2011/702853] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Accepted: 06/04/2011] [Indexed: 11/17/2022] Open
Abstract
Homocysteine (Hcy) has been recognized for the past five decades as a risk factor for atherosclerosis. However, the role of Hcy in the pathological changes associated with atherosclerosis as well as the pathological mechanisms triggered by Hcy accumulation is
poorly understood. Due to the reversal of the physiological direction of the reaction catalyzed by S-adenosyl-L-homocysteine
hydrolase Hcy accumulation leads to the synthesis of S-adenosyl-L-homocysteine (AdoHcy). AdoHcy is a strong product
inhibitor of S-adenosyl-L-methionine (AdoMet)-dependent methyltransferases, and to date more than 50 AdoMet-dependent
methyltransferases that methylate a broad spectrum of cellular compounds including nucleic acids, proteins and lipids have been
identified. Phospholipid methylation is the major consumer of AdoMet, both in mammals and in yeast. AdoHcy accumulation induced
either by Hcy supplementation or due to S-adenosyl-L-homocysteine hydrolase deficiency results in inhibition of phospholipid
methylation in yeast. Moreover, yeast cells accumulating AdoHcy also massively accumulate triacylglycerols (TAG). Similarly, Hcy
supplementation was shown to lead to increased TAG and sterol synthesis as well as to the induction of the unfolded protein
response (UPR) in mammalian cells. In this review a model of deregulation of lipid metabolism in response to accumulation of
AdoHcy in Hcy-associated pathology is proposed.
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Fakas S, Qiu Y, Dixon JL, Han GS, Ruggles KV, Garbarino J, Sturley SL, Carman GM. Phosphatidate phosphatase activity plays key role in protection against fatty acid-induced toxicity in yeast. J Biol Chem 2011; 286:29074-29085. [PMID: 21708942 DOI: 10.1074/jbc.m111.258798] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The PAH1-encoded phosphatidate (PA) phosphatase in Saccharomyces cerevisiae is a pivotal enzyme that produces diacylglycerol for the synthesis of triacylglycerol (TAG) and simultaneously controls the level of PA used for phospholipid synthesis. Quantitative lipid analysis showed that the pah1Δ mutation caused a reduction in TAG mass and an elevation in the mass of phospholipids and free fatty acids, changes that were more pronounced in the stationary phase. The levels of unsaturated fatty acids in the pah1Δ mutant were unaltered, although the ratio of palmitoleic acid to oleic acid was increased with a similar change in the fatty acid composition of phospholipids. The pah1Δ mutant exhibited classic hallmarks of apoptosis in stationary phase and a marked reduction in the quantity of cytoplasmic lipid droplets. Cells lacking PA phosphatase were sensitive to exogenous fatty acids in the order of toxicity palmitoleic acid > oleic acid > palmitic acid. In contrast, the growth of wild type cells was not inhibited by fatty acid supplementation. In addition, wild type cells supplemented with palmitoleic acid exhibited an induction in PA phosphatase activity and an increase in TAG synthesis. Deletion of the DGK1-encoded diacylglycerol kinase, which counteracts PA phosphatase in controlling PA content, suppressed the defect in lipid droplet formation in the pah1Δ mutant. However, the sensitivity of the pah1Δ mutant to palmitoleic acid was not rescued by the dgk1Δ mutation. Overall, these findings indicate a key role of PA phosphatase in TAG synthesis for protection against fatty acid-induced toxicity.
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Affiliation(s)
- Stylianos Fakas
- Department of Food Science, Rutgers University, New Brunswick, New Jersey 08901; Department of Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901 and
| | - Yixuan Qiu
- Department of Food Science, Rutgers University, New Brunswick, New Jersey 08901; Department of Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901 and
| | - Joseph L Dixon
- Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey 08901; Department of Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901 and
| | - Gil-Soo Han
- Department of Food Science, Rutgers University, New Brunswick, New Jersey 08901; Department of Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901 and
| | - Kelly V Ruggles
- Department of Pediatrics and Institute of Human Nutrition, Columbia University Medical Center, New York, New York 10032
| | - Jeanne Garbarino
- Department of Pediatrics and Institute of Human Nutrition, Columbia University Medical Center, New York, New York 10032
| | - Stephen L Sturley
- Department of Pediatrics and Institute of Human Nutrition, Columbia University Medical Center, New York, New York 10032
| | - George M Carman
- Department of Food Science, Rutgers University, New Brunswick, New Jersey 08901; Department of Rutgers Center for Lipid Research, Rutgers University, New Brunswick, New Jersey 08901 and.
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Chuang HH, Chen PT, Wang WN, Chen YT, Shaw JF. Functional proteomic analysis of rice bran esterases/lipases and characterization of a novel recombinant esterase. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:2019-2025. [PMID: 21322560 DOI: 10.1021/jf103972h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
An esterase from rice ( Oryza sativa ) bran was identified on two-dimensional gel using 4-methylumbelliferyl butyrate as a substrate. The esterase cDNA (870 bp) encoded a 289 amino acid protein (designated OsEST-b) and was expressed in Escherichia coli . The molecular weight of recombinant OsEST-b (rOsEST-b) was 27 kDa, as measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Biochemical characterization demonstrated that rOsEST-b was active over a broad temperature range (optimum at 60 °C) and preferred alkaline conditions (optimum at pH 9.0). The rOsEST-b showed maximum activity toward p-nitrophenyl butyrate (C(4)) among various p-nitrophenyl esters (C(4)-C(18)), indicating that rOsEST-b is an esterase for short-chain fatty acids. The kinetic parameters under optimal conditions were K(m) = 27.03 μM, k(cat) = 49 s(-1), and k(cat)/K(m) = 1.81 s(-1) μM(-1). The activity of rOsEST-b was not influenced by ethylenediaminetetraacetic acid, suggesting that it is not a metalloenzyme. The amino acid sequence analysis revealed that OsEST-b had a conserved pentapeptide esterase/lipase motif but that the essential active site serine (GXSXG) was replaced by cysteine (C). These results suggest that OsEST-b is distinct from traditional esterases/lipases and is a novel lipolytic enzyme in rice bran.
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Affiliation(s)
- Hsu-Han Chuang
- Department of Food Science and Biotechnology, National Chung Hsing University , Taichung 402, Taiwan
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Hill S, Hirano K, Shmanai VV, Marbois BN, Vidovic D, Bekish AV, Kay B, Tse V, Fine J, Clarke CF, Shchepinov MS. Isotope-reinforced polyunsaturated fatty acids protect yeast cells from oxidative stress. Free Radic Biol Med 2011; 50:130-8. [PMID: 20955788 PMCID: PMC3014413 DOI: 10.1016/j.freeradbiomed.2010.10.690] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 10/11/2010] [Accepted: 10/11/2010] [Indexed: 01/08/2023]
Abstract
The facile abstraction of bis-allylic hydrogens from polyunsaturated fatty acids (PUFAs) is the hallmark chemistry responsible for initiation and propagation of autoxidation reactions. The products of these autoxidation reactions can form cross-links to other membrane components and damage proteins and nucleic acids. We report that PUFAs deuterated at bis-allylic sites are much more resistant to autoxidation reactions, because of the isotope effect. This is shown using coenzyme Q-deficient Saccharomyces cerevisiae coq mutants with defects in the biosynthesis of coenzyme Q (Q). Q functions in respiratory energy metabolism and also functions as a lipid-soluble antioxidant. Yeast coq mutants incubated in the presence of the PUFA α-linolenic or linoleic acid exhibit 99% loss of colony formation after 4h, demonstrating a profound loss of viability. In contrast, coq mutants treated with monounsaturated oleic acid or with one of the deuterated PUFAs, 11,11-D(2)-linoleic or 11,11,14,14-D(4)-α-linolenic acid, retain viability similar to wild-type yeast. Deuterated PUFAs also confer protection to wild-type yeast subjected to heat stress. These results indicate that isotope-reinforced PUFAs are stabilized compared to standard PUFAs, and they protect coq mutants and wild-type yeast cells against the toxic effects of lipid autoxidation products. These findings suggest new approaches to controlling ROS-inflicted cellular damage and oxidative stress.
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Affiliation(s)
- Shauna Hill
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Kathleen Hirano
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Vadim V. Shmanai
- Institute of Physical Organic Chemistry of the National Academy of Sciences of Belarus, 13 Surganova Street, 220072 Belarus
| | - Beth N. Marbois
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Dragoslav Vidovic
- Department of Chemistry, Oxford University, South Parks Road, Oxford OX1 3QR, UK
| | - Andrei V. Bekish
- Department of Chemistry, Belarussian State University, Minsk 220030 Belarus
| | - Bradley Kay
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Vincent Tse
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Jonathan Fine
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Catherine F. Clarke
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
- To whom correspondence should be addressed: Catherine F. Clarke, UCLA Department of Chemistry and Biochemistry, 607 Charles E. Young Dr. E., Los Angeles CA 90095 Tel (310) 825-0771; Fax (310) 206-5213; ; and Mikhail S. Shchepinov, Retrotope, Inc. 12133 Foothill Lane, Los Altos Hills, CA 94022, USA (650)-917-9256; Fax (650)-917-9255;
| | - Mikhail S. Shchepinov
- Retrotope, Inc. 12133 Foothill Lane, Los Altos Hills, CA 94022, USA
- To whom correspondence should be addressed: Catherine F. Clarke, UCLA Department of Chemistry and Biochemistry, 607 Charles E. Young Dr. E., Los Angeles CA 90095 Tel (310) 825-0771; Fax (310) 206-5213; ; and Mikhail S. Shchepinov, Retrotope, Inc. 12133 Foothill Lane, Los Altos Hills, CA 94022, USA (650)-917-9256; Fax (650)-917-9255;
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Current awareness on yeast. Yeast 2010. [DOI: 10.1002/yea.1720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Smith AM, Ammar R, Nislow C, Giaever G. A survey of yeast genomic assays for drug and target discovery. Pharmacol Ther 2010; 127:156-64. [PMID: 20546776 DOI: 10.1016/j.pharmthera.2010.04.012] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 04/28/2010] [Indexed: 01/01/2023]
Abstract
Over the past decade, the development and application of chemical genomic assays using the model organism Saccharomyces cerevisiae has provided powerful methods to identify the mechanism of action of known drugs and novel small molecules in vivo. These assays identify drug target candidates, genes involved in buffering drug target pathways and also help to define the general cellular response to small molecules. In this review, we examine current yeast chemical genomic assays and summarize the potential applications of each approach.
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Affiliation(s)
- Andrew M Smith
- Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada
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Abstract
The endemic increase in lipid-associated disorders such as obesity and type 2 diabetes mellitus has placed triacylglycerol metabolism and its associated organelle, lipid droplets, in the spotlight of biomedical research. Key enzymes of triacylglycerol metabolism are structurally and functionally conserved between yeast and mammalian cells, and studies in yeast have contributed significantly to the understanding of their biological function(s). Based on these similarities, studies performed in yeast may provide further significant mechanistic insight into the molecular basis of triacylglycerol homeostasis and its important physiological roles in healthy and diseased cells.
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Affiliation(s)
- Sepp D Kohlwein
- Institute of Molecular Biosciences, University of Graz, A-8010 Graz, Austria.
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