1
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Yu Q, Zou W, Liu K, Sun J, Chao Y, Sun M, Zhang Q, Wang X, Wang X, Ge L. Lipid transport protein ORP2A promotes glucose signaling by facilitating RGS1 degradation. PLANT PHYSIOLOGY 2023; 192:3170-3188. [PMID: 37073508 DOI: 10.1093/plphys/kiad238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 03/16/2023] [Accepted: 04/18/2023] [Indexed: 05/03/2023]
Abstract
Heterotrimeric GTP-binding proteins (G proteins) are a group of regulators essential for signal transmission into cells. Regulator of G protein signaling 1 (AtRGS1) possesses intrinsic GTPase-accelerating protein (GAP) activity and could suppress G protein and glucose signal transduction in Arabidopsis (Arabidopsis thaliana). However, how AtRGS1 activity is regulated is poorly understood. Here, we identified a knockout mutant of oxysterol binding protein-related protein 2A, orp2a-1, which exhibits similar phenotypes to the arabidopsis g-protein beta 1-2 (agb1-2) mutant. Transgenic lines overexpressing ORP2A displayed short hypocotyls, a hypersensitive response to sugar, and lower intracellular AtRGS1 levels than the control. Consistently, ORP2A interacted with AtRGS1 in vitro and in vivo. Tissue-specific expression of 2 ORP2A alternative splicing isoforms implied functions in controlling organ size and shape. Bioinformatic data and phenotypes of orp2a-1, agb1-2, and the orp2a-1 agb1-2 double mutant revealed the genetic interactions between ORP2A and Gβ in the regulation of G protein signaling and sugar response. Both alternative protein isoforms of ORP2A localized in the endoplasmic reticulum (ER), plasma membrane (PM), and ER-PM contact sites and interacted with vesicle-associated membrane protein-associated protein 27-1 (VAP27-1) in vivo and in vitro through their two phenylalanines in an acidic track-like motif. ORP2A also displayed differential phosphatidyl phosphoinositide binding activity mediated by the pleckstrin homology domain in vitro. Taken together, the Arabidopsis membrane protein ORP2A interacts with AtRGS1 and VAP27-1 to positively regulate G protein and sugar signaling by facilitating AtRGS1 degradation.
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Affiliation(s)
- Qian Yu
- The Characteristic Laboratory of Crop Germplasm Innovation and Application, Provincial Department of Education, College of Agronomy, Qingdao Agricultural University, Qingdao 266109, China
| | - Wenjiao Zou
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China
- Institute of Pharmacy, Shandong University of Traditional Chinese Medicine, Jinan 250355, China
| | - Kui Liu
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China
- Shandong Provincial Key Laboratory of Biophysics, Dezhou University, Dezhou 253023, China
| | - Jialu Sun
- The Characteristic Laboratory of Crop Germplasm Innovation and Application, Provincial Department of Education, College of Agronomy, Qingdao Agricultural University, Qingdao 266109, China
| | - Yanru Chao
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China
| | - Mengyao Sun
- The Characteristic Laboratory of Crop Germplasm Innovation and Application, Provincial Department of Education, College of Agronomy, Qingdao Agricultural University, Qingdao 266109, China
| | - Qianqian Zhang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China
- Shandong Academy of Grape, Shandong Academy of Agricultural Sciences, Jinan 250100, China
| | - Xiaodong Wang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China
| | - Xiaofei Wang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China
| | - Lei Ge
- The Characteristic Laboratory of Crop Germplasm Innovation and Application, Provincial Department of Education, College of Agronomy, Qingdao Agricultural University, Qingdao 266109, China
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China
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2
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Enrich C, Lu A, Tebar F, Rentero C, Grewal T. Ca 2+ and Annexins - Emerging Players for Sensing and Transferring Cholesterol and Phosphoinositides via Membrane Contact Sites. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1422:393-438. [PMID: 36988890 DOI: 10.1007/978-3-031-21547-6_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Maintaining lipid composition diversity in membranes from different organelles is critical for numerous cellular processes. However, many lipids are synthesized in the endoplasmic reticulum (ER) and require delivery to other organelles. In this scenario, formation of membrane contact sites (MCS) between neighbouring organelles has emerged as a novel non-vesicular lipid transport mechanism. Dissecting the molecular composition of MCS identified phosphoinositides (PIs), cholesterol, scaffolding/tethering proteins as well as Ca2+ and Ca2+-binding proteins contributing to MCS functioning. Compelling evidence now exists for the shuttling of PIs and cholesterol across MCS, affecting their concentrations in distinct membrane domains and diverse roles in membrane trafficking. Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) at the plasma membrane (PM) not only controls endo-/exocytic membrane dynamics but is also critical in autophagy. Cholesterol is highly concentrated at the PM and enriched in recycling endosomes and Golgi membranes. MCS-mediated cholesterol transfer is intensely researched, identifying MCS dysfunction or altered MCS partnerships to correlate with de-regulated cellular cholesterol homeostasis and pathologies. Annexins, a conserved family of Ca2+-dependent phospholipid binding proteins, contribute to tethering and untethering events at MCS. In this chapter, we will discuss how Ca2+ homeostasis and annexins in the endocytic compartment affect the sensing and transfer of cholesterol and PIs across MCS.
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Affiliation(s)
- Carlos Enrich
- Departament de Biomedicina, Unitat de Biologia Cel⋅lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.
- Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.
| | - Albert Lu
- Departament de Biomedicina, Unitat de Biologia Cel⋅lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
| | - Francesc Tebar
- Departament de Biomedicina, Unitat de Biologia Cel⋅lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
| | - Carles Rentero
- Departament de Biomedicina, Unitat de Biologia Cel⋅lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain
| | - Thomas Grewal
- School of Pharmacy, Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia
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3
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Wilhelm LP, Wendling C, Védie B, Kobayashi T, Chenard MP, Tomasetto C, Drin G, Alpy F. STARD3 mediates endoplasmic reticulum-to-endosome cholesterol transport at membrane contact sites. EMBO J 2017; 36:1412-1433. [PMID: 28377464 PMCID: PMC5430228 DOI: 10.15252/embj.201695917] [Citation(s) in RCA: 161] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 03/03/2017] [Accepted: 03/06/2017] [Indexed: 01/04/2023] Open
Abstract
StAR‐related lipid transfer domain‐3 (STARD3) is a sterol‐binding protein that creates endoplasmic reticulum (ER)–endosome contact sites. How this protein, at the crossroad between sterol uptake and synthesis pathways, impacts the intracellular distribution of this lipid was ill‐defined. Here, by using in situ cholesterol labeling and quantification, we demonstrated that STARD3 induces cholesterol accumulation in endosomes at the expense of the plasma membrane. STARD3‐mediated cholesterol routing depends both on its lipid transfer activity and its ability to create ER–endosome contacts. Corroborating this, in vitro reconstitution assays indicated that STARD3 and its ER‐anchored partner, Vesicle‐associated membrane protein‐associated protein (VAP), assemble into a machine that allows a highly efficient transport of cholesterol within membrane contacts. Thus, STARD3 is a cholesterol transporter scaffolding ER–endosome contacts and modulating cellular cholesterol repartition by delivering cholesterol to endosomes.
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Affiliation(s)
- Léa P Wilhelm
- Functional Genomics and Cancer Department, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U 964, Illkirch, France.,Centre National de la Recherche Scientifique (CNRS), UMR 7104, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Corinne Wendling
- Functional Genomics and Cancer Department, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France.,Institut National de la Santé et de la Recherche Médicale (INSERM), U 964, Illkirch, France.,Centre National de la Recherche Scientifique (CNRS), UMR 7104, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Benoît Védie
- AP-HP (Assistance Publique - Hôpitaux de Paris), Hôpital Européen Georges Pompidou, Service de Biochimie, Paris, France
| | - Toshihide Kobayashi
- Université de Strasbourg, Illkirch, France.,Laboratory of Biophotonics and Pharmacology, Centre National de la Recherche Scientifique (CNRS), UMR 7213, Illkirch, France
| | - Marie-Pierre Chenard
- Functional Genomics and Cancer Department, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France.,Université de Strasbourg, Illkirch, France.,Service d'Anatomie Pathologique Générale, Centre Hospitalier Universitaire de Hautepierre, Strasbourg, France
| | - Catherine Tomasetto
- Functional Genomics and Cancer Department, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France .,Institut National de la Santé et de la Recherche Médicale (INSERM), U 964, Illkirch, France.,Centre National de la Recherche Scientifique (CNRS), UMR 7104, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Guillaume Drin
- Université Côte d'Azur, CNRS Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France
| | - Fabien Alpy
- Functional Genomics and Cancer Department, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France .,Institut National de la Santé et de la Recherche Médicale (INSERM), U 964, Illkirch, France.,Centre National de la Recherche Scientifique (CNRS), UMR 7104, Illkirch, France.,Université de Strasbourg, Illkirch, France
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4
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Alpy F, Tomasetto C. START ships lipids across interorganelle space. Biochimie 2014; 96:85-95. [DOI: 10.1016/j.biochi.2013.09.015] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 09/17/2013] [Indexed: 11/30/2022]
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5
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Alpy F, Legueux F, Bianchetti L, Tomasetto C. [START domain-containing proteins: a review of their role in lipid transport and exchange]. Med Sci (Paris) 2009; 25:181-91. [PMID: 19239851 DOI: 10.1051/medsci/2009252181] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Fifteen START domain-containing proteins exist in mammals. On the basis of their structural homology, this family is divided into several sub-families consisting mainly of non-vesicular intracellular lipid carriers. With the exception of the Thioesterase-START subfamily, the other subfamilies are represented among invertebrates. The START domain is always located in the C-terminus of the protein. It is a module of about 210 residues that binds lipids, including sterols. Cholesterol, 25-hydroxycholesterol, phosphatidylcholine, phosphatidylethanolamine and ceramides are ligands for STARD1/STARD3-6, STARD5, STARD2/STARD10, STARD10 and STARD11, respectively. The lipids or sterols bound by the remaining 7 START proteins are unknown. The START domain can be regarded as a lipid-exchange and/or a lipid-sensing domain. The START domain consists in a deep lipid-binding pocket--that shields the hydrophic ligand from the external aqueous environment--covered by a lid formed by a C-terminal alpha helix. Within the same subgroup, such as the sterols-carriers subgroup, different START domains have similar biochemical properties; however, their expression profile and their subcellular localization distinguish them and are critical for their different biological functions. START proteins act in a variety of distinct physiological processes, such as lipid transfer between intracellular compartments, lipid metabolism and modulation of signaling events. Mutation or misexpression of START proteins is linked to pathological processes, including genetic disorders, autoimmune diseases and cancers.
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Affiliation(s)
- Fabien Alpy
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Département de Biologie du Cancer, UPR 6520 CNRS/U964 Inserm/Université Louis Pasteur, BP10142, 67404 Illkirch, CU de Strasbourg, France
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6
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Hanada K, Kumagai K, Tomishige N, Yamaji T. CERT-mediated trafficking of ceramide. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:684-91. [PMID: 19416656 DOI: 10.1016/j.bbalip.2009.01.006] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 01/13/2009] [Accepted: 01/13/2009] [Indexed: 11/16/2022]
Abstract
The transport and sorting of lipids from the sites of their synthesis to their appropriate destinations are fundamental for membrane biogenesis. In the synthesis of sphingolipids in mammalian cells, ceramide is newly produced at the endoplasmic reticulum (ER), and transported from the ER to the trans Golgi regions, where it is converted to sphingomyelin. CERT mediates the ER-to-Golgi trafficking of ceramide. CERT contains several functional domains and motifs including i) a START domain capable of catalyzing inter-membrane transfer of ceramide, ii) a pleckstrin homology domain, which serves to target the Golgi apparatus, iii) a FFAT motif which interacts with the ER-resident membrane protein VAP, and iv) a serine-repeat motif, of which hyperphosphorylation down-regulates CERT activity. It has been suggested that CERT extracts ceramide from the ER and carries it to the Golgi apparatus in a non-vesicular manner and that efficient CERT-mediated trafficking of ceramide occurs at membrane contact sites between the ER and the Golgi apparatus.
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Affiliation(s)
- Kentaro Hanada
- Department of Biochemistry, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
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7
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Halter D, Neumann S, van Dijk SM, Wolthoorn J, de Mazière AM, Vieira OV, Mattjus P, Klumperman J, van Meer G, Sprong H. Pre- and post-Golgi translocation of glucosylceramide in glycosphingolipid synthesis. ACTA ACUST UNITED AC 2008; 179:101-15. [PMID: 17923531 PMCID: PMC2064740 DOI: 10.1083/jcb.200704091] [Citation(s) in RCA: 212] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Glycosphingolipids are controlled by the spatial organization of their metabolism and by transport specificity. Using immunoelectron microscopy, we localize to the Golgi stack the glycosyltransferases that produce glucosylceramide (GlcCer), lactosylceramide (LacCer), and GM3. GlcCer is synthesized on the cytosolic side and must translocate across to the Golgi lumen for LacCer synthesis. However, only very little natural GlcCer translocates across the Golgi in vitro. As GlcCer reaches the cell surface when Golgi vesicular trafficking is inhibited, it must translocate across a post-Golgi membrane. Concanamycin, a vacuolar proton pump inhibitor, blocks translocation independently of multidrug transporters that are known to translocate short-chain GlcCer. Concanamycin did not reduce LacCer and GM3 synthesis. Thus, GlcCer destined for glycolipid synthesis follows a different pathway and transports back into the endoplasmic reticulum (ER) via the late Golgi protein FAPP2. FAPP2 knockdown strongly reduces GM3 synthesis. Overall, we show that newly synthesized GlcCer enters two pathways: one toward the noncytosolic surface of a post-Golgi membrane and one via the ER toward the Golgi lumen LacCer synthase.
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Affiliation(s)
- David Halter
- Membrane Enzymology, Bijvoet Center, and Department of Cell Biology, University Medical Center Utrecht, Institute of Biomembranes, Utrecht University, 3584 Utrecht, Netherlands
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8
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Guo T, Gregg C, Boukh-Viner T, Kyryakov P, Goldberg A, Bourque S, Banu F, Haile S, Milijevic S, San KHY, Solomon J, Wong V, Titorenko VI. A signal from inside the peroxisome initiates its division by promoting the remodeling of the peroxisomal membrane. J Cell Biol 2007; 177:289-303. [PMID: 17438077 PMCID: PMC2064137 DOI: 10.1083/jcb.200609072] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Accepted: 03/19/2007] [Indexed: 12/21/2022] Open
Abstract
We define the dynamics of spatial and temporal reorganization of the team of proteins and lipids serving peroxisome division. The peroxisome becomes competent for division only after it acquires the complete set of matrix proteins involved in lipid metabolism. Overloading the peroxisome with matrix proteins promotes the relocation of acyl-CoA oxidase (Aox), an enzyme of fatty acid beta-oxidation, from the matrix to the membrane. The binding of Aox to Pex16p, a membrane-associated peroxin required for peroxisome biogenesis, initiates the biosynthesis of phosphatidic acid and diacylglycerol (DAG) in the membrane. The formation of these two lipids and the subsequent transbilayer movement of DAG initiate the assembly of a complex between the peroxins Pex10p and Pex19p, the dynamin-like GTPase Vps1p, and several actin cytoskeletal proteins on the peroxisomal surface. This protein team promotes membrane fission, thereby executing the terminal step of peroxisome division.
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Affiliation(s)
- Tong Guo
- Department of Biology, Concordia University, Montreal, Quebec H4B 1R6, Canada
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9
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Puglielli L. Aging of the brain, neurotrophin signaling, and Alzheimer's disease: is IGF1-R the common culprit? Neurobiol Aging 2007; 29:795-811. [PMID: 17313996 PMCID: PMC2387053 DOI: 10.1016/j.neurobiolaging.2007.01.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 09/21/2006] [Accepted: 01/13/2007] [Indexed: 12/26/2022]
Abstract
The last decade has revealed that the lifespan of an organism can be modulated by the signaling pathway that acts downstream of the insulin/insulin-like growth factor 1 receptors (IR/IGF1-R), indicating that there is a "program" that drives the process of aging. New results have now linked the same pathway to the neurogenic capacities of the aging brain, to neurotrophin signaling, and to the molecular pathogenesis of Alzheimer's disease. Therefore, a common signaling cascade now seems to link aging to age-associated pathologies of the brain, suggesting that pharmacologic approaches aimed at the modulation of this pathway can serve to delay the onset of age-associated disorders and improve the quality of life. Work from a wide range of fields performed with different approaches has already identified some of the signaling molecules that act downstream of IGF1-R, and has revealed that a delicate checkpoint exists to balance excessive growth/"immortality" and reduced growth/"senescence" of a cell. Future research will determine how far the connection goes and how much of it we can influence.
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Affiliation(s)
- Luigi Puglielli
- Department of Medicine, University of Wisconsin-Madison, and Geriatric Research Education Clinical Center, VA Medical Center, VAH-GRECC 11G, 2500 Overlook Terrace, Madison, WI 53705, USA.
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10
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Hanada K, Kumagai K, Tomishige N, Kawano M. CERT and intracellular trafficking of ceramide. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:644-53. [PMID: 17314061 DOI: 10.1016/j.bbalip.2007.01.009] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Revised: 01/12/2007] [Accepted: 01/13/2007] [Indexed: 02/07/2023]
Abstract
The transport and sorting of lipids from the sites of their synthesis to their appropriate destinations are fundamental for membrane biogenesis. In the synthesis of sphingolipids in mammalian cells, ceramide is newly produced at the endoplasmic reticulum (ER), and transported from the ER to the trans Golgi regions, where it is converted to sphingomyelin. CERT has been identified as a key factor for the ER-to-Golgi trafficking of ceramide. CERT contains several functional domains including (i) a START domain capable of catalyzing inter-membrane transfer of ceramide, (ii) a pleckstrin homology domain, which serves to target the Golgi apparatus by recognizing phosphatidylinositol 4-monophosphate, and (iii) a short peptide motif named FFAT motif which interacts with the ER-resident membrane protein VAP. CERT is preferentially distributed to the Golgi region in cells, and Golgi-targeted CERT appears to retain the activity to interact with VAP. On the basis of these results, it has been proposed that CERT extracts ceramide from the ER and carries it to the Golgi apparatus in a non-vesicular manner and that a particularly efficient cycle of CERT movement for trafficking of ceramide may proceed at membrane contact sites between the ER and the Golgi apparatus.
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Affiliation(s)
- Kentaro Hanada
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo, 162-8640, Japan.
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11
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Chang TY, Chang CCY, Ohgami N, Yamauchi Y. Cholesterol sensing, trafficking, and esterification. Annu Rev Cell Dev Biol 2006; 22:129-57. [PMID: 16753029 DOI: 10.1146/annurev.cellbio.22.010305.104656] [Citation(s) in RCA: 438] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mammalian cells acquire cholesterol from low-density lipoprotein (LDL) and from endogenous biosynthesis. The roles of the Niemann-Pick type C1 protein in mediating the endosomal transport of LDL-derived cholesterol and endogenously synthesized cholesterol are discussed. Excess cellular cholesterol is converted to cholesteryl esters by the enzyme acyl-coenzyme A:cholesterol acyltransferase (ACAT) 1 or is removed from a cell by cellular cholesterol efflux at the plasma membrane. A close relationship between the ACAT substrate pool and the cholesterol efflux pool is proposed. Sterol-sensing domains (SSDs) are present in several membrane proteins, including NPC1, HMG-CoA reductase, and the SREBP cleavage-activating protein. The functions of SSDs are described. ACAT1 is an endoplasmic reticulum cholesterol sensor and contains a signature motif characteristic of the membrane-bound acyltransferase family. The nonvesicular cholesterol translocation processes involve the START domain proteins and the oxysterol binding protein-related proteins (ORPs). The properties of these proteins are summarized.
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Affiliation(s)
- Ta-Yuan Chang
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
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12
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Hanada K. Discovery of the molecular machinery CERT for endoplasmic reticulum-to-Golgi trafficking of ceramide. Mol Cell Biochem 2006; 286:23-31. [PMID: 16601923 DOI: 10.1007/s11010-005-9044-z] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Synthesis and sorting of lipids are essential events for membrane biogenesis and its homeostasis. Ceramide is synthesised at the endoplasmic reticulum (ER), and translocated to the Golgi compartment for conversion to sphingomyelin (SM). We have recently identified a key factor (named CERT) for ceramide trafficking. In this short review, I summarise recent advances in molecular mechanisms of intracellular transport of ceramide, focusing on our genetic and biochemical approaches to this issue.
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Affiliation(s)
- Kentaro Hanada
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, 1-23-1, Toyama, Tokyo 162-8640, Japan.
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13
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Alpy F, Tomasetto C. Give lipids a START: the StAR-related lipid transfer (START) domain in mammals. J Cell Sci 2005; 118:2791-801. [PMID: 15976441 DOI: 10.1242/jcs.02485] [Citation(s) in RCA: 285] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The steroidogenic acute regulatory protein (StAR)-related lipid transfer (START) domain is a protein module of approximately 210 residues that binds lipids, including sterols. Fifteen mammalian proteins, STARD1-STARD15, possess a START domain and these can be grouped into six subfamilies. Cholesterol, 25-hydroxycholesterol, phosphatidylcholine, phosphatidylethanolamine and ceramides are ligands for STARD1/STARD3/STARD5, STARD5, STARD2/STARD10, STARD10 and STARD11, respectively. The lipids or sterols bound by the remaining 9 START proteins are unknown. Recent studies show that the C-terminal end of the domain plays a fundamental role, forming a lid over a deep lipid-binding pocket that shields the ligand from the external environment. The START domain can be regarded as a lipid-exchange and/or a lipid-sensing domain. Mammalian START proteins have diverse expression patterns and can be found free in the cytoplasm, attached to membranes or in the nucleus. They appear to function in a variety of distinct physiological processes, such as lipid transfer between intracellular compartments, lipid metabolism and modulation of signaling events. Mutation or misexpression of START proteins is linked to pathological processes, including genetic disorders, autoimmune disease and cancer.
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Affiliation(s)
- Fabien Alpy
- Inserm, U682 Strasbourg, F67200, Development and Physiopathology of the Intestine and Pancreas, University Louis Pasteur, Strasbourg, France
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14
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Wang P, Zhang Y, Li H, Chieu HK, Munn AL, Yang H. AAA ATPases regulate membrane association of yeast oxysterol binding proteins and sterol metabolism. EMBO J 2005; 24:2989-99. [PMID: 16096648 PMCID: PMC1201346 DOI: 10.1038/sj.emboj.7600764] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2004] [Accepted: 07/13/2005] [Indexed: 11/09/2022] Open
Abstract
The yeast genome encodes seven oxysterol binding protein homologs, Osh1p-Osh7p, which have been implicated in regulating intracellular lipid and vesicular transport. Here, we show that both Osh6p and Osh7p interact with Vps4p, a member of the AAA (ATPases associated with a variety of cellular activities) family. The coiled-coil domain of Osh7p was found to interact with Vps4p in a yeast two-hybrid screen and the interaction between Osh7p and Vps4p appears to be regulated by ergosterol. Deletion of VPS4 induced a dramatic increase in the membrane-associated pools of Osh6p and Osh7p and also caused a decrease in sterol esterification, which was suppressed by overexpression of OSH7. Lastly, overexpression of the coiled-coil domain of Osh7p (Osh7pCC) resulted in a multivesicular body sorting defect, suggesting a dominant negative role of Osh7pCC possibly through inhibiting Vps4p function. Our data suggest that a common mechanism may exist for AAA proteins to regulate the membrane association of yeast OSBP proteins and that these two protein families may function together to control subcellular lipid transport.
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Affiliation(s)
- Penghua Wang
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, Singapore, Singapore
| | - Yong Zhang
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, Singapore, Singapore
| | - Hongzhe Li
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, Singapore, Singapore
| | - Hai Kee Chieu
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, Singapore, Singapore
| | - Alan L Munn
- Institute of Molecular and Cell Biology, A*STAR Biomedical Research Institutes, Singapore, Singapore
- Institute for Molecular Bioscience and ARC Special Research Centre for Functional and Applied Genomics, The University of Queensland, St Lucia, Queensland, Australia
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Hongyuan Yang
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, National University of Singapore, Singapore 119260, Singapore. Tel.: +65 687 47996; Fax: +65 677 91453; E-mail:
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15
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Wang PY, Weng J, Anderson RGW. OSBP is a cholesterol-regulated scaffolding protein in control of ERK 1/2 activation. Science 2005; 307:1472-6. [PMID: 15746430 DOI: 10.1126/science.1107710] [Citation(s) in RCA: 235] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Oxysterol-binding protein (OSBP) is the founding member of a family of sterol-binding proteins implicated in vesicle transport, lipid metabolism, and signal transduction. Here, OSBP was found to function as a cholesterol-binding scaffolding protein coordinating the activity of two phosphatases to control the extracellular signal-regulated kinase (ERK) signaling pathway. Cytosolic OSBP formed a approximately 440-kilodalton oligomer with a member of the PTPPBS family of tyrosine phosphatases, the serine/threonine phosphatase PP2A, and cholesterol. This oligomer had dual specific phosphatase activity for phosphorylated ERK (pERK). When cell cholesterol was lowered, the oligomer disassembled and the level of pERK rose. The oligomer also disassembled when exposed to oxysterols. Increasing the amount of OSBP oligomer rendered cells resistant to the effects of cholesterol depletion and decreased the basal level of pERK. Thus, cholesterol functions through its interaction with OSBP outside of membranes to regulate the assembly of an oligomeric phosphatase that controls a key signaling pathway in the cell.
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Affiliation(s)
- Ping-Yuan Wang
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA
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16
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Affiliation(s)
- Gagan D Gupta
- National Centre for Biological Sciences,UAS-GKVK Campus, Bangalore 560 065, India.
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17
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Ikonen E. Genetics and molecular biology. Curr Opin Lipidol 2004; 15:219-21. [PMID: 15017366 DOI: 10.1097/00041433-200404000-00016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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18
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Wu CC, MacCoss MJ, Mardones G, Finnigan C, Mogelsvang S, Yates JR, Howell KE. Organellar proteomics reveals Golgi arginine dimethylation. Mol Biol Cell 2004; 15:2907-19. [PMID: 15047867 PMCID: PMC420113 DOI: 10.1091/mbc.e04-02-0101] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Golgi complex functions to posttranslationally modify newly synthesized proteins and lipids and to sort them to their sites of function. In this study, a stacked Golgi fraction was isolated by classical cell fractionation, and the protein complement (the Golgi proteome) was characterized using multidimensional protein identification technology. Many of the proteins identified are known residents of the Golgi, and 64% of these are predicted transmembrane proteins. Proteins localized to other organelles also were identified, strengthening reports of functional interfacing between the Golgi and the endoplasmic reticulum and cytoskeleton. Importantly, 41 proteins of unknown function were identified. Two were selected for further analysis, and Golgi localization was confirmed. One of these, a putative methyltransferase, was shown to be arginine dimethylated, and upon further proteomic analysis, arginine dimethylation was identified on 18 total proteins in the Golgi proteome. This survey illustrates the utility of proteomics in the discovery of novel organellar functions and resulted in 1) a protein profile of an enriched Golgi fraction; 2) identification of 41 previously uncharacterized proteins, two with confirmed Golgi localization; 3) the identification of arginine dimethylated residues in Golgi proteins; and 4) a confirmation of methyltransferase activity within the Golgi fraction.
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Affiliation(s)
- Christine C Wu
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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