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Xu Z, Tong Q, Lv W, Xiao Y, Wang Z. Phosphocholine cytidylyltransferase MoPct1 is crucial for vegetative growth, conidiation, and appressorium-mediated plant infection by Magnaporthe oryzae. Front Microbiol 2023; 14:1136168. [PMID: 37213497 PMCID: PMC10196169 DOI: 10.3389/fmicb.2023.1136168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 04/12/2023] [Indexed: 05/23/2023] Open
Abstract
Phosphatidylcholine (PC) plays crucial biological roles in eukaryotic cells. In Saccharomyces cerevisiae, apart from phosphatidylethanolamine (PE) methylation pathway, PC is also synthesized via CDP-choline pathway. Phosphocholine cytidylyltransferase Pct1 is the rate-limiting enzyme to catalyze the conversion from phosphocholine to CDP-choline in this pathway. Here, we report the identification and functional characterization of an ortholog of the budding yeast PCT1 in Magnaporthe oryzae, named MoPCT1. Targeted gene deletion mutants of MoPCT1 were impaired in vegetative growth, conidiation, appressorium turgor accumulation and cell wall integrity. Also, the mutants were severely compromised in appressorium-mediated penetration, infectious growth and pathogenicity. Western blot analysis revealed that cell autophagy was activated by the deletion of MoPCT1 under nutrient-rich conditions. Moreover, we found several key genes in PE methylation pathway, such as MoCHO2, MoOPI3, and MoPSD2, were significantly up-regulated in the ΔMopct1 mutants, indicating that a pronounced compensation effect exists between the two PC biosynthesis pathways in M. oryzae. Interestingly, in the ΔMopct1 mutants, histone H3 was hypermethylated and expression levels of several methionine cycling-related genes were significantly up-regulated, suggesting that MoPCT1 is involved in histone H3 methylation and methionine metabolism. Taken together, we conclude that the phosphocholine cytidylyltransferase coding gene MoPCT1 plays important roles in vegetative growth, conidiation and appressorium-mediated plant infection by M. oryzae.
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Tavasoli M, Lahire S, Reid T, Brodovsky M, McMaster CR. Genetic diseases of the Kennedy pathways for membrane synthesis. J Biol Chem 2020; 295:17877-17886. [PMID: 33454021 PMCID: PMC7762932 DOI: 10.1074/jbc.rev120.013529] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 10/20/2020] [Indexed: 11/06/2022] Open
Abstract
The two branches of the Kennedy pathways (CDP-choline and CDP-ethanolamine) are the predominant pathways responsible for the synthesis of the most abundant phospholipids, phosphatidylcholine and phosphatidylethanolamine, respectively, in mammalian membranes. Recently, hereditary diseases associated with single gene mutations in the Kennedy pathways have been identified. Interestingly, genetic diseases within the same pathway vary greatly, ranging from muscular dystrophy to spastic paraplegia to a childhood blinding disorder to bone deformations. Indeed, different point mutations in the same gene (PCYT1; CCTα) result in at least three distinct diseases. In this review, we will summarize and review the genetic diseases associated with mutations in genes of the Kennedy pathway for phospholipid synthesis. These single-gene disorders provide insight, indeed direct genotype-phenotype relationships, into the biological functions of specific enzymes of the Kennedy pathway. We discuss potential mechanisms of how mutations within the same pathway can cause disparate disease.
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Affiliation(s)
- Mahtab Tavasoli
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Sarah Lahire
- University of Reims Champagne-Ardenne, Reims, France
| | - Taryn Reid
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Maren Brodovsky
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
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3
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Izrael R, Marton L, Nagy GN, Pálinkás HL, Kucsma N, Vértessy BG. Identification of a nuclear localization signal in the Plasmodium falciparum CTP: phosphocholine cytidylyltransferase enzyme. Sci Rep 2020; 10:19739. [PMID: 33184408 PMCID: PMC7665022 DOI: 10.1038/s41598-020-76829-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 11/02/2020] [Indexed: 12/30/2022] Open
Abstract
The phospholipid biosynthesis of the malaria parasite, Plasmodium falciparum is a key process for its survival and its inhibition is a validated antimalarial therapeutic approach. The second and rate-limiting step of the de novo phosphatidylcholine biosynthesis is catalysed by CTP: phosphocholine cytidylyltransferase (PfCCT), which has a key regulatory function within the pathway. Here, we investigate the functional impact of the key structural differences and their respective role in the structurally unique pseudo-heterodimer PfCCT protein in a heterologous cellular context using the thermosensitive CCT-mutant CHO-MT58 cell line. We found that a Plasmodium-specific lysine-rich insertion within the catalytic domain of PfCCT acts as a nuclear localization signal and its deletion decreases the nuclear propensity of the protein in the model cell line. We further showed that the putative membrane-binding domain also affected the nuclear localization of the protein. Moreover, activation of phosphatidylcholine biosynthesis by phospholipase C treatment induces the partial nuclear-to-cytoplasmic translocation of PfCCT. We additionally investigated the cellular function of several PfCCT truncated constructs in a CHO-MT58 based rescue assay. In absence of the endogenous CCT activity we observed that truncated constructs lacking the lysine-rich insertion, or the membrane-binding domain provided similar cell survival ratio as the full length PfCCT protein.
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Affiliation(s)
- Richard Izrael
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary.
- Doctoral School of Multidisciplinary Medical Sciences, University of Szeged, 6720, Szeged, Hungary.
- Department of Applied Biotechnology, Budapest University of Technology and Economics, 1111, Budapest, Hungary.
| | - Lívia Marton
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary
| | - Gergely N Nagy
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary
- Department of Applied Biotechnology, Budapest University of Technology and Economics, 1111, Budapest, Hungary
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Hajnalka L Pálinkás
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary
- Doctoral School of Multidisciplinary Medical Sciences, University of Szeged, 6720, Szeged, Hungary
- Department of Applied Biotechnology, Budapest University of Technology and Economics, 1111, Budapest, Hungary
| | - Nóra Kucsma
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary
| | - Beáta G Vértessy
- Institute of Enzymology, Research Centre for Natural Sciences, 1117, Budapest, Hungary.
- Department of Applied Biotechnology, Budapest University of Technology and Economics, 1111, Budapest, Hungary.
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4
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Wang S, Idrissi FZ, Hermansson M, Grippa A, Ejsing CS, Carvalho P. Seipin and the membrane-shaping protein Pex30 cooperate in organelle budding from the endoplasmic reticulum. Nat Commun 2018; 9:2939. [PMID: 30054465 PMCID: PMC6063905 DOI: 10.1038/s41467-018-05278-2] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 06/18/2018] [Indexed: 11/20/2022] Open
Abstract
Lipid droplets (LDs) and peroxisomes are ubiquitous organelles with central roles in eukaryotic cells. Although the mechanisms involved in biogenesis of these organelles remain elusive, both seem to require the endoplasmic reticulum (ER). Here we show that in yeast the ER budding of these structurally unrelated organelles has remarkably similar requirements and involves cooperation between Pex30 and the seipin complex. In the absence of these components, budding of both LDs and peroxisomes is inhibited, leading to the ER accumulation of their respective constituent molecules, such as triacylglycerols and peroxisomal membrane proteins, whereas COPII vesicle formation remains unaffected. This phenotype can be reversed by remodeling ER phospholipid composition highlighting a key function of these lipids in organelle biogenesis. We propose that seipin and Pex30 act in concert to organize membrane domains permissive for organelle budding, and that may have a lipid composition distinct from the bulk ER.
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Affiliation(s)
- Sihui Wang
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
| | - Fatima-Zahra Idrissi
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Dr. Aiguader, 88, 08003, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Dr. Aiguader, 88, 08003, Barcelona, Spain
| | - Martin Hermansson
- Department of Biochemistry and Molecular Biology, Villum Center for Bioanalytical Sciences, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark
| | - Alexandra Grippa
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Dr. Aiguader, 88, 08003, Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Dr. Aiguader, 88, 08003, Barcelona, Spain
| | - Christer S Ejsing
- Department of Biochemistry and Molecular Biology, Villum Center for Bioanalytical Sciences, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Pedro Carvalho
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK.
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Dr. Aiguader, 88, 08003, Barcelona, Spain.
- Universitat Pompeu Fabra (UPF), Dr. Aiguader, 88, 08003, Barcelona, Spain.
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5
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Haider A, Wei YC, Lim K, Barbosa AD, Liu CH, Weber U, Mlodzik M, Oras K, Collier S, Hussain MM, Dong L, Patel S, Alvarez-Guaita A, Saudek V, Jenkins BJ, Koulman A, Dymond MK, Hardie RC, Siniossoglou S, Savage DB. PCYT1A Regulates Phosphatidylcholine Homeostasis from the Inner Nuclear Membrane in Response to Membrane Stored Curvature Elastic Stress. Dev Cell 2018; 45:481-495.e8. [PMID: 29754800 PMCID: PMC5971203 DOI: 10.1016/j.devcel.2018.04.012] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 02/27/2018] [Accepted: 04/11/2018] [Indexed: 12/19/2022]
Abstract
Cell and organelle membranes consist of a complex mixture of phospholipids (PLs) that determine their size, shape, and function. Phosphatidylcholine (PC) is the most abundant phospholipid in eukaryotic membranes, yet how cells sense and regulate its levels in vivo remains unclear. Here we show that PCYT1A, the rate-limiting enzyme of PC synthesis, is intranuclear and re-locates to the nuclear membrane in response to the need for membrane PL synthesis in yeast, fly, and mammalian cells. By aligning imaging with lipidomic analysis and data-driven modeling, we demonstrate that yeast PCYT1A membrane association correlates with membrane stored curvature elastic stress estimates. Furthermore, this process occurs inside the nucleus, although nuclear localization signal mutants can compensate for the loss of endogenous PCYT1A in yeast and in fly photoreceptors. These data suggest an ancient mechanism by which nucleoplasmic PCYT1A senses surface PL packing defects on the inner nuclear membrane to control PC homeostasis.
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Affiliation(s)
- Afreen Haider
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Yu-Chen Wei
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Koini Lim
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Antonio D Barbosa
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Che-Hsiung Liu
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
| | - Ursula Weber
- Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York City, NY 10029, USA
| | - Marek Mlodzik
- Department of Cell, Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, New York City, NY 10029, USA
| | - Kadri Oras
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - Simon Collier
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - M Mahmood Hussain
- Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Liang Dong
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Satish Patel
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Anna Alvarez-Guaita
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Vladimir Saudek
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Benjamin J Jenkins
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Albert Koulman
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Marcus K Dymond
- Division of Chemistry, School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton BN2 4GJ, UK
| | - Roger C Hardie
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3EG, UK
| | - Symeon Siniossoglou
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK.
| | - David B Savage
- Metabolic Research Laboratories, Wellcome Trust-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK.
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6
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McMaster CR. From yeast to humans - roles of the Kennedy pathway for phosphatidylcholine synthesis. FEBS Lett 2017; 592:1256-1272. [PMID: 29178478 DOI: 10.1002/1873-3468.12919] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 10/20/2017] [Accepted: 11/06/2017] [Indexed: 12/13/2022]
Abstract
The major phospholipid present in most eukaryotic membranes is phosphatidylcholine (PC), comprising ~ 50% of phospholipid content. PC metabolic pathways are highly conserved from yeast to humans. The main pathway for the synthesis of PC is the Kennedy (CDP-choline) pathway. In this pathway, choline is converted to phosphocholine by choline kinase, phosphocholine is metabolized to CDP-choline by the rate-determining enzyme for this pathway, CTP:phosphocholine cytidylyltransferase, and cholinephosphotransferase condenses CDP-choline with diacylglycerol to produce PC. This Review discusses how PC synthesis via the Kennedy pathway is regulated, its role in cellular and biological processes, as well as diseases known to be associated with defects in PC synthesis. Finally, we present the first model for the making of a membrane via PC synthesis.
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7
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Grippa A, Buxó L, Mora G, Funaya C, Idrissi FZ, Mancuso F, Gomez R, Muntanyà J, Sabidó E, Carvalho P. The seipin complex Fld1/Ldb16 stabilizes ER-lipid droplet contact sites. J Cell Biol 2015; 211:829-44. [PMID: 26572621 PMCID: PMC4657162 DOI: 10.1083/jcb.201502070] [Citation(s) in RCA: 148] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 10/16/2015] [Indexed: 01/11/2023] Open
Abstract
Mutations in the seipin complex components Fld1 and Ldb16 result in the loss of lipid droplet identity and phospholipid packing defects, revealing a role of this complex in the stabilization of ER–lipid droplet contact sites. Lipid droplets (LDs) are storage organelles consisting of a neutral lipid core surrounded by a phospholipid monolayer and a set of LD-specific proteins. Most LD components are synthesized in the endoplasmic reticulum (ER), an organelle that is often physically connected with LDs. How LD identity is established while maintaining biochemical and physical connections with the ER is not known. Here, we show that the yeast seipin Fld1, in complex with the ER membrane protein Ldb16, prevents equilibration of ER and LD surface components by stabilizing the contact sites between the two organelles. In the absence of the Fld1/Ldb16 complex, assembly of LDs results in phospholipid packing defects leading to aberrant distribution of lipid-binding proteins and abnormal LDs. We propose that the Fld1/Ldb16 complex facilitates the establishment of LD identity by acting as a diffusion barrier at the ER–LD contact sites.
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Affiliation(s)
- Alexandra Grippa
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Laura Buxó
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Gabriel Mora
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Charlotta Funaya
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Fatima-Zahra Idrissi
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Francesco Mancuso
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Raul Gomez
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Júlia Muntanyà
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
| | - Eduard Sabidó
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Pedro Carvalho
- Centre for Genomic Regulation, The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain Universitat Pompeu Fabra, 08003 Barcelona, Spain
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8
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Barbosa AD, Sembongi H, Su WM, Abreu S, Reggiori F, Carman GM, Siniossoglou S. Lipid partitioning at the nuclear envelope controls membrane biogenesis. Mol Biol Cell 2015; 26:3641-57. [PMID: 26269581 PMCID: PMC4603934 DOI: 10.1091/mbc.e15-03-0173] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 07/22/2015] [Accepted: 08/06/2015] [Indexed: 12/11/2022] Open
Abstract
Partitioning of lipid precursors between membranes and storage is crucial for cell growth, and its disruption underlies pathologies such as cancer, obesity, and type 2 diabetes. However, the mechanisms and signals that regulate this process are largely unknown. In yeast, lipid precursors are mainly used for phospholipid synthesis in nutrient-rich conditions in order to sustain rapid proliferation but are redirected to triacylglycerol (TAG) stored in lipid droplets during starvation. Here we investigate how cells reprogram lipid metabolism in the endoplasmic reticulum. We show that the conserved phosphatidate (PA) phosphatase Pah1, which generates diacylglycerol from PA, targets a nuclear membrane subdomain that is in contact with growing lipid droplets and mediates TAG synthesis. We find that cytosol acidification activates the master regulator of Pah1, the Nem1-Spo7 complex, thus linking Pah1 activity to cellular metabolic status. In the absence of TAG storage capacity, Pah1 still binds the nuclear membrane, but lipid precursors are redirected toward phospholipids, resulting in nuclear deformation and a proliferation of endoplasmic reticulum membrane. We propose that, in response to growth signals, activation of Pah1 at the nuclear envelope acts as a switch to control the balance between membrane biogenesis and lipid storage.
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Affiliation(s)
- Antonio Daniel Barbosa
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Hiroshi Sembongi
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Wen-Min Su
- Department of Food Science and the Rutgers Center for Lipid Research, New Jersey Institute for Food, Nutrition and Health, Rutgers University, New Brunswick, NJ 08901
| | - Susana Abreu
- Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 A Groningen, Netherlands
| | - Fulvio Reggiori
- Department of Cell Biology, University Medical Center Groningen, University of Groningen, 9713 A Groningen, Netherlands
| | - 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, NJ 08901
| | - Symeon Siniossoglou
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, United Kingdom
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9
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Cornell RB, Ridgway ND. CTP:phosphocholine cytidylyltransferase: Function, regulation, and structure of an amphitropic enzyme required for membrane biogenesis. Prog Lipid Res 2015; 59:147-71. [PMID: 26165797 DOI: 10.1016/j.plipres.2015.07.001] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 07/07/2015] [Accepted: 07/07/2015] [Indexed: 12/12/2022]
Abstract
CTP:phosphocholine cytidylyltransferase (CCT) catalyzes a rate-limiting and regulated step in the CDP-choline pathway for the synthesis of phosphatidylcholine (PC) and PC-derived lipids. Control of CCT activity is multi-layered, and includes direct regulation by reversible membrane binding involving a built-in lipid compositional sensor. Thus CCT contributes to phospholipid compositional homeostasis. CCT also modifies the curvature of its target membrane. Knowledge of CCT structure and regulation of its catalytic function are relatively advanced compared to many lipid metabolic enzymes, and are reviewed in detail. Recently the genetic origins of two human developmental and lipogenesis disorders have been traced to mutations in the gene for CCTα.
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Affiliation(s)
- Rosemary B Cornell
- Department of Molecular Biology and Biochemistry and the Department of Chemistry, Simon Fraser University, Burnaby, B.C. V5A-1S6, Canada.
| | - Neale D Ridgway
- Departments of Pediatrics, and Biochemistry and Molecular Biology, Atlantic Research Centre, Dalhousie University, Halifax, Nova Scotia B3H-4H7, Canada
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10
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Checks and balances in membrane phospholipid class and acyl chain homeostasis, the yeast perspective. Prog Lipid Res 2013; 52:374-94. [PMID: 23631861 DOI: 10.1016/j.plipres.2013.04.006] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 03/28/2013] [Accepted: 04/16/2013] [Indexed: 11/24/2022]
Abstract
Glycerophospholipids are the most abundant membrane lipid constituents in most eukaryotic cells. As a consequence, phospholipid class and acyl chain homeostasis are crucial for maintaining optimal physical properties of membranes that in turn are crucial for membrane function. The topic of this review is our current understanding of membrane phospholipid homeostasis in the reference eukaryote Saccharomyces cerevisiae. After introducing the physical parameters of the membrane that are kept in optimal range, the properties of the major membrane phospholipids and their contributions to membrane structure and dynamics are summarized. Phospholipid metabolism and known mechanisms of regulation are discussed, including potential sensors for monitoring membrane physical properties. Special attention is paid to processes that maintain the phospholipid class specific molecular species profiles, and to the interplay between phospholipid class and acyl chain composition when yeast membrane lipid homeostasis is challenged. Based on the reviewed studies, molecular species selectivity of the lipid metabolic enzymes, and mass action in acyl-CoA metabolism are put forward as important intrinsic contributors to membrane lipid homeostasis.
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11
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Siniossoglou S. Phospholipid metabolism and nuclear function: Roles of the lipin family of phosphatidic acid phosphatases. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:575-81. [DOI: 10.1016/j.bbalip.2012.09.014] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 09/19/2012] [Accepted: 09/24/2012] [Indexed: 01/22/2023]
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12
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Abstract
There is increasing evidence that certain Vacuolar protein sorting (Vps) proteins, factors that mediate vesicular protein trafficking, have additional roles in regulating transcription factors at the endosome. We found that yeast mutants lacking the phosphatidylinositol 3-phosphate [PI(3)P] kinase Vps34 or its associated protein kinase Vps15 display multiple phenotypes indicating impaired transcription elongation. These phenotypes include reduced mRNA production from long or G+C-rich coding sequences (CDS) without affecting the associated GAL1 promoter activity, and a reduced rate of RNA polymerase II (Pol II) progression through lacZ CDS in vivo. Consistent with reported genetic interactions with mutations affecting the histone acetyltransferase complex NuA4, vps15Δ and vps34Δ mutations reduce NuA4 occupancy in certain transcribed CDS. vps15Δ and vps34Δ mutants also exhibit impaired localization of the induced GAL1 gene to the nuclear periphery. We found unexpectedly that, similar to known transcription elongation factors, these and several other Vps factors can be cross-linked to the CDS of genes induced by Gcn4 or Gal4 in a manner dependent on transcriptional induction and stimulated by Cdk7/Kin28-dependent phosphorylation of the Pol II C-terminal domain (CTD). We also observed colocalization of a fraction of Vps15-GFP and Vps34-GFP with nuclear pores at nucleus-vacuole (NV) junctions in live cells. These findings suggest that Vps factors enhance the efficiency of transcription elongation in a manner involving their physical proximity to nuclear pores and transcribed chromatin.
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13
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Phosphatidylcholine and the CDP-choline cycle. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1831:523-32. [PMID: 23010477 DOI: 10.1016/j.bbalip.2012.09.009] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 09/16/2012] [Indexed: 11/20/2022]
Abstract
The CDP-choline pathway of phosphatidylcholine (PtdCho) biosynthesis was first described more than 50 years ago. Investigation of the CDP-choline pathway in yeast provides a basis for understanding the CDP-choline pathway in mammals. PtdCho is considered as an intermediate in a cycle of synthesis and degradation, and the activity of a CDP-choline cycle is linked to subcellular membrane lipid movement. The components of the mammalian CDP-choline pathway include choline transport, choline kinase, phosphocholine cytidylyltransferase, and choline phosphotransferase activities. The protein isoforms and biochemical mechanisms of regulation of the pathway enzymes are related to their cell- and tissue-specific functions. Regulated PtdCho turnover mediated by phospholipases or neuropathy target esterase participates in the mammalian CDP-choline cycle. Knockout mouse models define the biological functions of the CDP-choline cycle in mammalian cells and tissues. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.
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14
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Schneiter R, Cole CN. Integrating complex functions: coordination of nuclear pore complex assembly and membrane expansion of the nuclear envelope requires a family of integral membrane proteins. Nucleus 2012; 1:387-92. [PMID: 21326820 DOI: 10.4161/nucl.1.5.12333] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Revised: 04/14/2010] [Accepted: 04/23/2010] [Indexed: 11/19/2022] Open
Abstract
The nuclear envelope harbors numerous large proteinaceous channels, the nuclear pore complexes (NPCs), through which macromolecular exchange between the cytosol and the nucleoplasm occurs. This double-membrane nuclear envelope is continuous with the endoplasmic reticulum and thus functionally connected to such diverse processes as vesicular transport, protein maturation and lipid synthesis. Recent results obtained from studies in Saccharomyces cerevisiae indicate that assembly of the nuclear pore complex is functionally dependent upon maintenance of lipid homeostasis of the ER membrane. Previous work from one of our laboratories has revealed that an integral membrane protein Apq12 is important for the assembly of functional nuclear pores. Cells lacking APQ12 are viable but cannot grow at low temperatures, have aberrant NPCs and a defect in mRNA export. Remarkably, these defects in NPC assembly can be overcome by supplementing cells with a membrane fluidizing agent, benzyl alcohol, suggesting that Apq12 impacts the flexibility of the nuclear membrane, possibly by adjusting its lipid composition when cells are shifted to a reduced temperature. Our new study now expands these findings and reveals that an essential membrane protein, Brr6, shares at least partially overlapping functions with Apq12 and is also required for assembly of functional NPCs. A third nuclear envelope membrane protein, Brl1, is related to Brr6, and is also required for NPC assembly. Because maintenance of membrane homeostasis is essential for cellular survival, the fact that these three proteins are conserved in fungi that undergo closed mitoses, but are not found in metazoans or plants, may indicate that their functions are performed by proteins unrelated at the primary sequence level to Brr6, Brl1 and Apq12 in cells that disassemble their nuclear envelopes during mitosis.
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Affiliation(s)
- Roger Schneiter
- Division of Biochemistry, Department of Medicine, University of Fribourg, Fribourg, Switzerland.
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Kupke T, Di Cecco L, Müller HM, Neuner A, Adolf F, Wieland F, Nickel W, Schiebel E. Targeting of Nbp1 to the inner nuclear membrane is essential for spindle pole body duplication. EMBO J 2011; 30:3337-52. [PMID: 21785410 DOI: 10.1038/emboj.2011.242] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Accepted: 06/30/2011] [Indexed: 12/29/2022] Open
Abstract
Spindle pole bodies (SPBs), like nuclear pore complexes, are embedded in the nuclear envelope (NE) at sites of fusion of the inner and outer nuclear membranes. A network of interacting proteins is required to insert a cytoplasmic SPB precursor into the NE. A central player of this network is Nbp1 that interacts with the conserved integral membrane protein Ndc1. Here, we establish that Nbp1 is a monotopic membrane protein that is essential for SPB insertion at the inner face of the NE. In vitro and in vivo studies identified an N-terminal amphipathic α-helix of Nbp1 as a membrane-binding element, with crucial functions in SPB duplication. The karyopherin Kap123 binds to a nuclear localization sequence next to this amphipathic α-helix and prevents unspecific tethering of Nbp1 to membranes. After transport into the nucleus, Nbp1 binds to the inner nuclear membrane. These data define the targeting pathway of a SPB component and suggest that the amphipathic α-helix of Nbp1 is important for SPB insertion into the NE from within the nucleus.
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Affiliation(s)
- Thomas Kupke
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Heidelberg, Germany
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