201
|
Wriessnegger T, Pichler H. Yeast metabolic engineering – Targeting sterol metabolism and terpenoid formation. Prog Lipid Res 2013; 52:277-93. [DOI: 10.1016/j.plipres.2013.03.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Revised: 03/26/2013] [Accepted: 03/27/2013] [Indexed: 12/28/2022]
|
202
|
Tong J, Yang H, Yang H, Eom SH, Im YJ. Structure of Osh3 reveals a conserved mode of phosphoinositide binding in oxysterol-binding proteins. Structure 2013; 21:1203-13. [PMID: 23791945 DOI: 10.1016/j.str.2013.05.007] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 04/25/2013] [Accepted: 05/08/2013] [Indexed: 11/27/2022]
Abstract
The oxysterol-binding protein (OSBP)-related proteins (ORPs) are conserved from yeast to humans, and implicated in the regulation of lipid homeostasis and in signaling pathways. Saccharomyces cerevisiae has seven ORPs (Osh1-Osh7) that share one unknown essential function. Here, we report the 1.5-2.3 Å structures of the PH domain and ORD (OSBP-related domain) of yeast Osh3 in apo-form or in complex with phosphatidylinositol 4-phosphate (PI[4]P). Osh3 recognizes PI(4)P by the highly conserved residues in the tunnel of ORD whereas it lacks sterol binding due to the narrow hydrophobic tunnel. Yeast complementation tests suggest that PI(4)P binding to PH and ORD is essential for function. This study suggests that the unifying feature in all ORP homologs is the binding of PI(4)P to ORD and sterol binding is additional to certain homologs. Structural modeling of full-length Osh3 is consistent with the concept that Osh3 is a lipid transfer protein or regulator in membrane contact sites.
Collapse
Affiliation(s)
- Junsen Tong
- College of Pharmacy, Chonnam National University, Gwangju 500-757, South Korea
| | | | | | | | | |
Collapse
|
203
|
Sheng R, Chen Y, Yung Gee H, Stec E, Melowic HR, Blatner NR, Tun MP, Kim Y, Källberg M, Fujiwara TK, Hye Hong J, Pyo Kim K, Lu H, Kusumi A, Goo Lee M, Cho W. Cholesterol modulates cell signaling and protein networking by specifically interacting with PDZ domain-containing scaffold proteins. Nat Commun 2013; 3:1249. [PMID: 23212378 PMCID: PMC3526836 DOI: 10.1038/ncomms2221] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 10/22/2012] [Indexed: 02/06/2023] Open
Abstract
Cholesterol is known to modulate the physical properties of cell membranes but its direct involvement in cellular signaling has not been thoroughly investigated. Here we show that cholesterol specifically binds many PDZ domains found in scaffold proteins, including the N-terminal PDZ domain of NHERF1/EBP50. This modular domain has a cholesterol-binding site topologically distinct from its canonical protein-binding site and serves as a dual specificity domain that bridges the membrane and juxta-membrane signaling complexes. Disruption of the cholesterol binding activity of NHERF1 largely abrogates its dynamic colocalization with and activation of cystic fibrosis transmembrane conductance regulator, one of its binding partners in the plasma membrane of mammalian cells. At least seven more PDZ domains from other scaffold proteins also bind cholesterol and have cholesterol-binding sites, suggesting that cholesterol modulates cell signaling through direct interactions with these scaffold proteins. This mechanism may provide an alternative explanation for the formation of signaling platforms in cholesterol-rich membrane domains.
Collapse
Affiliation(s)
- Ren Sheng
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
204
|
Kim YJ, Hernandez MLG, Balla T. Inositol lipid regulation of lipid transfer in specialized membrane domains. Trends Cell Biol 2013; 23:270-8. [PMID: 23489878 PMCID: PMC3665726 DOI: 10.1016/j.tcb.2013.01.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 01/22/2013] [Accepted: 01/31/2013] [Indexed: 11/22/2022]
Abstract
The highly dynamic membranous network of eukaryotic cells allows spatial organization of biochemical reactions to suit the complex metabolic needs of the cell. The unique lipid composition of organelle membranes in the face of dynamic membrane activities assumes that lipid gradients are constantly generated and maintained. Important advances have been made in identifying specialized membrane compartments and lipid transfer mechanisms that are critical for generating and maintaining lipid gradients. Remarkably, one class of minor phospholipids--the phosphoinositides--is emerging as important regulators of these processes. Here, we summarize several lines of research that have led to our current understanding of the connection between phosphoinositides and the transport of structural lipids and offer some thoughts on general principles possibly governing these processes.
Collapse
Affiliation(s)
- Yeun Ju Kim
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Maria-Luisa Guzman Hernandez
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| |
Collapse
|
205
|
Wang L, Yang Y, Hong B. Advances in the role of microRNAs in lipid metabolism-related anti-atherosclerotic drug discovery. Expert Opin Drug Discov 2013; 8:977-90. [DOI: 10.1517/17460441.2013.798639] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
206
|
LeBlanc MA, Fairn GD, Russo SB, Czyz O, Zaremberg V, Cowart LA, McMaster CR. The yeast oxysterol binding protein Kes1 maintains sphingolipid levels. PLoS One 2013; 8:e60485. [PMID: 23593226 PMCID: PMC3617146 DOI: 10.1371/journal.pone.0060485] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 02/27/2013] [Indexed: 01/24/2023] Open
Abstract
The oxysterol binding protein family are amphitropic proteins that bind oxysterols, sterols, and possibly phosphoinositides, in a conserved binding pocket. The Saccharomyces cerevisiae oxysterol binding protein family member Kes1 (also known as Osh4) also binds phosphoinositides on a distinct surface of the protein from the conserved binding pocket. In this study, we determine that the oxysterol binding protein family member Kes1 is required to maintain the ratio of complex sphingolipids and levels of ceramide, sphingosine-phosphate and sphingosine. This inability to maintain normal sphingolipid homeostasis resulted in misdistribution of Pma1, a protein that requires normal sphingolipid synthesis to occur to partition into membrane rafts at the Golgi for its trafficking to the plasma membrane.
Collapse
Affiliation(s)
- Marissa A. LeBlanc
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Gregory D. Fairn
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Sarah B. Russo
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, United States of America
| | - Ola Czyz
- Department of Biology, University of Calgary, Calgary, Alberta, Canada
| | - Vanina Zaremberg
- Department of Biology, University of Calgary, Calgary, Alberta, Canada
| | - L. Ashley Cowart
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, United States of America
- Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina, United States of America
| | | |
Collapse
|
207
|
Stefan CJ, Manford AG, Emr SD. ER-PM connections: sites of information transfer and inter-organelle communication. Curr Opin Cell Biol 2013; 25:434-42. [PMID: 23522446 DOI: 10.1016/j.ceb.2013.02.020] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 02/25/2013] [Accepted: 02/28/2013] [Indexed: 11/18/2022]
Abstract
Eukaryotic cells are divided into distinct membrane-bound organelles with unique identities and specialized metabolic functions. Communication between organelles must take place to regulate the size, shape, and composition of individual organelles, as well as to coordinate transport between organelles. The endoplasmic reticulum (ER) forms an expansive membrane network that contacts and participates in crosstalk with several other organelles in the cell, most notably the plasma membrane (PM). ER-PM junctions have well-established functions in the movement of small molecules, such as lipids and ions, between the ER and PM. Recent discoveries have revealed additional exciting roles for ER-PM junctions in the regulation of cell signaling, ER shape and architecture, and PM domain organization.
Collapse
Affiliation(s)
- Christopher J Stefan
- Weill Institute for Cell & Molecular Biology, Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY 14853, United States.
| | | | | |
Collapse
|
208
|
Telang A, Rechel JA, Brandt JR, Donnell DM. Analysis of ovary-specific genes in relation to egg maturation and female nutritional condition in the mosquitoes Georgecraigius atropalpus and Aedes aegypti (Diptera: Culicidae). JOURNAL OF INSECT PHYSIOLOGY 2013; 59:283-94. [PMID: 23238126 PMCID: PMC3596486 DOI: 10.1016/j.jinsphys.2012.11.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 11/23/2012] [Accepted: 11/27/2012] [Indexed: 05/09/2023]
Abstract
Analysis of the reproductive physiology of anautogenous mosquitoes at the molecular level is complicated by the simultaneity of ovarian maturation and the digestion of a blood meal. In contrast to anautogenous mosquitoes, autogenous female mosquitoes can acquire greater nutrient stores as larvae and exhibit higher ovarian production of ecdysteroids at adult eclosion. These features essentially replace the role of a blood meal in provisioning the first batch of eggs and initiating egg development. To gain insight into the process of ovary maturation we first performed a transcript analysis of the obligatory autogenous mosquito Georgecraigius atropalpus (formerly Ochlerotatus atropalpus). We identified ESTs using suppressive subtractive hybridization (SSH) of transcripts from ovaries at critical times during oogenesis in the absence of blood digestion. Preliminary expression studies of genes such as apolipophorin III (APO) and oxysterol binding protein (OSBP) suggested these genes might be cued to female nutritional status. We then applied our findings to the medically important anautogenous mosquito Aedes aegypti. RNAi-based analyses of these genes in Ae. aegypti revealed a reduction in APO transcripts leads to reduced lipid levels in carcass and ovaries and that OSBP may play a role in overall lipid and sterol homeostasis. In addition to expanding our understanding of mosquito ovarian development, the continued use of a comparative approach between autogenous and anautogenous species may provide novel intervention points for the regulation of mosquito egg production.
Collapse
Affiliation(s)
- Aparna Telang
- Department of Biology, University of Richmond, Richmond, VA 23173, USA.
| | | | | | | |
Collapse
|
209
|
Weber-Boyvat M, Zhong W, Yan D, Olkkonen VM. Oxysterol-binding proteins: functions in cell regulation beyond lipid metabolism. Biochem Pharmacol 2013; 86:89-95. [PMID: 23428468 DOI: 10.1016/j.bcp.2013.02.016] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 02/08/2013] [Accepted: 02/11/2013] [Indexed: 12/12/2022]
Abstract
Oxysterol-binding (OSBP)-related proteins (ORPs) constitute a family of sterol and phosphoinositide binding/transfer proteins in eukaryotes from yeast to man. While their functions have mainly been addressed in cellular lipid metabolism or sterol transport, increasing evidence points to more versatile regulatory roles in a spectrum of cellular regimes. In fact ORPs do not appear to be robust controllers of lipid homeostasis. Several ORPs localize at membrane contacts sites (MCS), where endoplasmic reticulum (ER) is apposed with other organelle limiting membranes. Apparently, ORPs have the capacity to control the formation of MCS or activity of enzymatic machineries at these sites. Thereby, ORPs most likely affect organelle membrane lipid compositions, with impacts on signaling and vesicle transport, but also cellular lipid metabolism. Moreover, an increasing number of protein interaction partners of ORPs have been identified, connecting these proteins with various aspects of cell regulation. Small molecular anti-proliferative compounds, ORPphilins, were recently found to target two members of the ORP family, OSBP and ORP4, revealing an essential function of ORPs in cancer cell proliferation and survival. Further functions assigned for ORPs include regulation of extracellular signal regulated kinase (ERK) activity (OSBP), control of ER-late endosome MCS and late endosome motility (ORP1L), regulation of β1-integrin activity (ORP3), modulation of hepatocyte insulin signaling and macrophage migration (ORP8), as well as post-Golgi vesicle transport, phosphatidylinositol-4-phosphate and target of rapamycin complex 1 signaling and nitrogen sensing (Saccharomyces cerevisiae Osh4p). These and other recent observations shed light on the ORPs as integrators of lipid signals with an unforeseen variety of vital cellular processes.
Collapse
Affiliation(s)
- Marion Weber-Boyvat
- Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290 Helsinki, Finland
| | | | | | | |
Collapse
|
210
|
Helle SCJ, Kanfer G, Kolar K, Lang A, Michel AH, Kornmann B. Organization and function of membrane contact sites. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2526-41. [PMID: 23380708 DOI: 10.1016/j.bbamcr.2013.01.028] [Citation(s) in RCA: 329] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Revised: 01/18/2013] [Accepted: 01/21/2013] [Indexed: 11/16/2022]
Abstract
Membrane-bound organelles are a wonderful evolutionary acquisition of the eukaryotic cell, allowing the segregation of sometimes incompatible biochemical reactions into specific compartments with tailored microenvironments. On the flip side, these isolating membranes that crowd the interior of the cell, constitute a hindrance to the diffusion of metabolites and information to all corners of the cell. To ensure coordination of cellular activities, cells use a network of contact sites between the membranes of different organelles. These membrane contact sites (MCSs) are domains where two membranes come to close proximity, typically less than 30nm. Such contacts create microdomains that favor exchange between two organelles. MCSs are established and maintained in durable or transient states by tethering structures, which keep the two membranes in proximity, but fusion between the membranes does not take place. Since the endoplasmic reticulum (ER) is the most extensive cellular membrane network, it is thus not surprising to find the ER involved in most MCSs within the cell. The ER contacts diverse compartments such as mitochondria, lysosomes, lipid droplets, the Golgi apparatus, endosomes and the plasma membrane. In this review, we will focus on the common organizing principles underlying the many MCSs found between the ER and virtually all compartments of the cell, and on how the ER establishes a network of MCSs for the trafficking of vital metabolites and information. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
Collapse
Affiliation(s)
- Sebastian C J Helle
- Institute of Biochemistry, ETH Zürich, HPM G16 Schafmattstrasse, Zürich, Switzerland
| | | | | | | | | | | |
Collapse
|
211
|
Bigay J, Antonny B. Curvature, lipid packing, and electrostatics of membrane organelles: defining cellular territories in determining specificity. Dev Cell 2013; 23:886-95. [PMID: 23153485 DOI: 10.1016/j.devcel.2012.10.009] [Citation(s) in RCA: 358] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Whereas some rare lipids contribute to the identity of cell organelles, we focus on the abundant lipids that form the matrix of organelle membranes. Observations using bioprobes and peripheral proteins, notably sensors of membrane curvature, support the prediction that the cell contains two broad membrane territories: the territory of loose lipid packing, where cytosolic proteins take advantage of membrane defects, and the territory of electrostatics, where proteins are attracted by negatively charged lipids. The contrasting features of these territories provide specificity for reactions occurring along the secretory pathway, on the plasma membrane, and also on lipid droplets and autophagosomes.
Collapse
Affiliation(s)
- Joëlle Bigay
- Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia Antipolis et CNRS, 06560 Valbonne, France
| | | |
Collapse
|
212
|
Du X, Yang H. Endosomal cholesterol trafficking: protein factors at a glance. Acta Biochim Biophys Sin (Shanghai) 2013; 45:11-7. [PMID: 23165745 DOI: 10.1093/abbs/gms095] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The delivery of low-density lipoprotein-derived cholesterol (LDL-C) from endosomal compartments to the plasma membrane and the endoplasmic reticulum (ER) is an important yet poorly understood cellular process. Niemann-Pick C1 (NPC1), a multi-pass integral membrane protein on the limiting membranes of late endosomes (LE)/lysosomes (Ly), is known to insert lumenal LDL-C to the limiting membrane of LE/Ly. Recent progress has identified novel cytoplasmic proteins that regulate the exit of LDL-C from LE/Ly, such as ORP5, a member of the oxysterol-binding protein-related protein (ORPs) family, and Hrs/VPS27, a well-established regulator of the endosomal sorting complex required for transport pathway. Whereas ORP5/ORPs may serve as cytosolic cholesterol carriers and deliver cholesterol in a non-vesicular manner, how Hrs/VPS27 regulate endosomal cholesterol sorting remains enigmatic. We discuss the functional relationship between NPC1, Hrs, and ORP5, and formulate possible schemes on how LDL-C may be moved from endosomal compartments to other cellular organelles.
Collapse
Affiliation(s)
- Ximing Du
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, Australia
| | | |
Collapse
|
213
|
Tong J, Yang H, Ha S, Lee Y, Eom SH, Im YJ. Crystallization and preliminary X-ray crystallographic analysis of the oxysterol-binding protein Osh3 from Saccharomyces cerevisiae. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012; 68:1498-502. [PMID: 23192032 PMCID: PMC3509973 DOI: 10.1107/s1744309112042510] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 10/10/2012] [Indexed: 11/10/2022]
Abstract
Oxysterol-binding protein (OSBP) related proteins (ORPs) are conserved from yeast to humans and are implicated in regulation of sterol homeostasis and in signal transduction pathways. Osh3 of Saccharomyces cerevisiae is a pleckstrin-homology (PH) domain-containing ORP member that regulates phosphoinositide metabolism at endoplasmic reticulum-plasma membrane contact sites. The N-terminal PH domain of Osh3 was purified and crystallized as a lysozyme fusion and the resulting crystal diffracted to 2.3 Å resolution. The crystal belonged to the monoclinic space group C2, with unit-cell parameters a=98.03, b=91.31, c=84.13 Å, β=81.41°. With two molecules in the asymmetric unit, the Matthews coefficient was 3.13 Å3 Da(-1). Initial attempts to solve the structure by molecular-replacement techniques using T4 lysozyme as a search model were successful. The C-terminal OSBP-related domain (OBD) of Osh3 was crystallized by the vapour-diffusion method and the resulting crystal diffracted to 1.5 Å resolution. The crystal was orthorhombic, belonging to space group P2(1)2(1)2(1), with unit-cell parameters a=41.57, b=87.52, c=100.58 Å. With one molecule in the asymmetric unit, the Matthews coefficient was 2.01 Å3 Da(-1). Initial attempts to solve the structure by the single-wavelength anomalous dispersion technique using bromine were successful.
Collapse
Affiliation(s)
- Junsen Tong
- College of Pharmacy, Chonnam National University, Gwangju 500-757, Republic of Korea
| | - Huiseon Yang
- College of Pharmacy, Chonnam National University, Gwangju 500-757, Republic of Korea
| | - Subin Ha
- College of Pharmacy, Chonnam National University, Gwangju 500-757, Republic of Korea
| | - Youngjin Lee
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Soo Hyun Eom
- Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
| | - Young Jun Im
- College of Pharmacy, Chonnam National University, Gwangju 500-757, Republic of Korea
| |
Collapse
|
214
|
Membrane-Binding Mechanism of a Peripheral Membrane Protein through Microsecond Molecular Dynamics Simulations. J Mol Biol 2012; 423:847-61. [DOI: 10.1016/j.jmb.2012.08.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 08/16/2012] [Accepted: 08/20/2012] [Indexed: 11/22/2022]
|
215
|
Du X, Kazim AS, Dawes IW, Brown AJ, Yang H. The AAA ATPase VPS4/SKD1 Regulates Endosomal Cholesterol Trafficking Independently of ESCRT-III. Traffic 2012; 14:107-19. [DOI: 10.1111/tra.12015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 09/21/2012] [Accepted: 09/25/2012] [Indexed: 01/31/2023]
Affiliation(s)
- Ximing Du
- School of Biotechnology and Biomolecular Sciences; The University of New South Wales; Sydney NSW 2052 Australia
| | - Abdulla S. Kazim
- School of Biotechnology and Biomolecular Sciences; The University of New South Wales; Sydney NSW 2052 Australia
| | - Ian W. Dawes
- School of Biotechnology and Biomolecular Sciences; The University of New South Wales; Sydney NSW 2052 Australia
| | - Andrew J. Brown
- School of Biotechnology and Biomolecular Sciences; The University of New South Wales; Sydney NSW 2052 Australia
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences; The University of New South Wales; Sydney NSW 2052 Australia
| |
Collapse
|
216
|
Benned-Jensen T, Norn C, Laurent S, Madsen CM, Larsen HM, Arfelt KN, Wolf RM, Frimurer T, Sailer AW, Rosenkilde MM. Molecular characterization of oxysterol binding to the Epstein-Barr virus-induced gene 2 (GPR183). J Biol Chem 2012; 287:35470-35483. [PMID: 22875855 PMCID: PMC3471686 DOI: 10.1074/jbc.m112.387894] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2012] [Indexed: 11/06/2022] Open
Abstract
Oxysterols are oxygenated cholesterol derivates that are emerging as a physiologically important group of molecules. Although they regulate a range of cellular processes, only few oxysterol-binding effector proteins have been identified, and the knowledge of their binding mode is limited. Recently, the family of G protein-coupled seven transmembrane-spanning receptors (7TM receptors) was added to this group. Specifically, the Epstein-Barr virus-induced gene 2 (EBI2 or GPR183) was shown to be activated by several oxysterols, most potently by 7α,25-dihydroxycholesterol (7α,25-OHC). Nothing is known about the binding mode, however. Using mutational analysis, we identify here four key residues for 7α,25-OHC binding: Arg-87 in TM-II (position II:20/2.60), Tyr-112 and Tyr-116 (positions III:09/3.33 and III:13/3.37) in TM-III, and Tyr-260 in TM-VI (position VI:16/6.51). Substituting these residues with Ala and/or Phe results in a severe decrease in agonist binding and receptor activation. Docking simulations suggest that Tyr-116 interacts with the 3β-OH group in the agonist, Tyr-260 with the 7α-OH group, and Arg-87, either directly or indirectly, with the 25-OH group, although nearby residues likely also contribute. In addition, Tyr-112 is involved in 7α,25-OHC binding but via hydrophobic interactions. Finally, we show that II:20/2.60 constitutes an important residue for ligand binding in receptors carrying a positively charged residue at this position. This group is dominated by lipid- and nucleotide-activated receptors, here exemplified by the CysLTs, P2Y12, and P2Y14. In conclusion, we present the first molecular characterization of oxysterol binding to a 7TM receptor and identify position II:20/2.60 as a generally important residue for ligand binding in certain 7TM receptors.
Collapse
Affiliation(s)
- Tau Benned-Jensen
- Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Christoffer Norn
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Stephane Laurent
- Developmental and Molecular Pathways, Novartis Institutes for BioMedical Research, 4056 Basel, Switzerland
| | - Christian M Madsen
- Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Hjalte M Larsen
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Kristine N Arfelt
- Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Romain M Wolf
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, 4056 Basel, Switzerland
| | - Thomas Frimurer
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark; Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Andreas W Sailer
- Developmental and Molecular Pathways, Novartis Institutes for BioMedical Research, 4056 Basel, Switzerland
| | - Mette M Rosenkilde
- Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark.
| |
Collapse
|
217
|
Abstract
PURPOSE OF REVIEW To offer a comprehensive review on the roles that oxysterols synthesized or engulfed by macrophages, or oxysterol-binding proteins in these cells, play in the development and progression of atherosclerotic lesions. RECENT FINDINGS Oxysterols abundant within the plaque have the capacity to potentiate macrophage proinflammatory signaling and to induce cell death. These activities may contribute to formation of the complex lesion, expansion of the necrotic core, and to plaque rupture. On the contrary, several endogenous oxysterols generated by cholesterol hydroxylases act as ligands of liver X receptors, stimulate macrophage cholesterol efflux, repress proinflammatory signaling, and promote macrophage survival, counteracting lesion progression. Cytoplasmic oxysterol-binding proteins represent a family of sterol and phosphoinositide sensors that may contribute to the regulatory impact of these bioactive lipids on processes relevant in the context of atherogenesis. SUMMARY The generation and deposition of oxysterols within the developing plaque is envisioned to modulate macrophage lipid metabolism, to affect the delicate balance of proinflammatory and anti-inflammatory processes, and to impact cell fate decisions, thus, determining whether the lesion remains benign or whether it develops into a hazardous, vulnerable plaque.
Collapse
Affiliation(s)
- Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research bInstitute of Biomedicine, Anatomy, University of Helsinki, Helsinki, Finland.
| |
Collapse
|
218
|
Abstract
The transport of lipids from their synthesis site at the endoplasmic reticulum (ER) to different target membranes could be mediated by both vesicular and nonvesicular transport mechanisms. Nonvesicular lipid transport appears to be the major transport route of certain lipid species, and could be mediated by either spontaneous lipid transport or by lipid-transfer proteins (LTPs). Although nonvesicular lipid transport has been extensively studied for more than four decades, its underlying mechanism, advantage and regulation, have not been fully explored. In particular, the function of LTPs and their involvement in intracellular lipid movement remain largely controversial. In this article, we describe the pathways by which lipids are synthesized at the ER and delivered to different cellular membranes, and discuss the role of LTPs in lipid transport both in vitro and in intact cells.
Collapse
Affiliation(s)
- Sima Lev
- Molecular Cell Biology Department, Weizmann Institute of Science, Rehovot 76100, Israel.
| |
Collapse
|
219
|
Pathogen-Related Yeast (PRY) proteins and members of the CAP superfamily are secreted sterol-binding proteins. Proc Natl Acad Sci U S A 2012; 109:16882-7. [PMID: 23027975 DOI: 10.1073/pnas.1209086109] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Sterols and related membrane-perturbing agents are subject to a quality control cycle. Compounds that fail to pass this control are acetylated and secreted into the culture media, whereas lipids that pass the cycle are deacetylated and retained within the cell. Here we describe the identification of a family of conserved proteins, the Pathogen-Related Yeast (PRY) proteins, as a class of sterol-binding proteins. Saccharomyces cerevisiae has three members of this family, two of which, Pry1 and Pry2, are secreted, whereas Pry3 is a cell wall-associated protein. Cells lacking both PRY1 and PRY2 have a complete block in secretion of the acetylated lipid and Pry1 and Pry2 proteins bind free cholesterol and cholesteryl acetate in vitro. PRY proteins belong to a large protein superfamily of unknown mode of action, the CAP protein superfamily [i.e. cysteine-rich secretory proteins (CRISP), antigen 5, and pathogenesis related 1 proteins]. The conserved CAP domain of Pry1 is necessary and sufficient for lipid export and sterol binding. Expression of a human CAP superfamily member, the cysteine-rich secretory protein 2 (CRISP2), rescues the phenotype of yeast mutants lacking Pry function and purified CRISP2 binds cholesterol in vitro, indicating that lipid binding is a conserved function of the CAP superfamily proteins.
Collapse
|
220
|
Abstract
The striking morphology of the Golgi complex has fascinated cell biologists since its discovery over 100 years ago. Yet, despite intense efforts to understand how membrane flow relates to Golgi form and function, this organelle continues to baffle cell biologists and biochemists alike. Fundamental questions regarding Golgi function, while hotly debated, remain unresolved. Historically, Golgi function has been described from a protein-centric point of view, but we now appreciate that conceptual frameworks for how lipid metabolism is integrated with Golgi biogenesis and function are essential for a mechanistic understanding of this fascinating organelle. It is from a lipid-centric perspective that we discuss the larger question of Golgi dynamics and membrane trafficking. We review the growing body of evidence for how lipid metabolism is integrally written into the engineering of the Golgi system and highlight questions for future study.
Collapse
Affiliation(s)
- Vytas A Bankaitis
- Department of Cell and Developmental Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7090, USA.
| | | | | |
Collapse
|
221
|
Goto A, Liu X, Robinson CA, Ridgway ND. Multisite phosphorylation of oxysterol-binding protein regulates sterol binding and activation of sphingomyelin synthesis. Mol Biol Cell 2012; 23:3624-35. [PMID: 22875984 PMCID: PMC3442410 DOI: 10.1091/mbc.e12-04-0283] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The endoplasmic reticulum (ER)-Golgi sterol transfer activity of oxysterol-binding protein (OSBP) regulates sphingomyelin (SM) synthesis, as well as post-Golgi cholesterol efflux pathways. The phosphorylation and ER-Golgi localization of OSBP are correlated, suggesting this modification regulates the directionality and/or specificity of transfer activity. In this paper, we report that phosphorylation on two serine-rich motifs, S381-S391 (site 1) and S192, S195, S200 (site 2), specifically controls OSBP activity at the ER. A phosphomimetic of the SM/cholesterol-sensitive phosphorylation site 1 (OSBP-S5E) had increased in vitro cholesterol and 25-hydroxycholesterol-binding capacity, and cholesterol extraction from liposomes, but reduced transfer activity. Phosphatidylinositol 4-phosphate (PI(4)P) and cholesterol competed for a common binding site on OSBP; however, direct binding of PI(4)P was not affected by site 1 phosphorylation. Individual site 1 and site 2 phosphomutants supported oxysterol activation of SM synthesis in OSBP-deficient CHO cells. However, a double site1/2 mutant (OSBP-S381A/S3D) was deficient in this activity and was constitutively colocalized with vesicle-associated membrane protein-associated protein A (VAP-A) in a collapsed ER network. This study identifies phosphorylation regulation of sterol and VAP-A binding by OSBP in the ER, and PI(4)P as an alternate ligand that could be exchanged for sterol in the Golgi apparatus.
Collapse
Affiliation(s)
- Asako Goto
- Department of Pediatrics, Atlantic Research Centre, Dalhousie University, Halifax, NS, Canada
| | | | | | | |
Collapse
|
222
|
Stappenbeck F, Xiao W, Epperson M, Riley M, Priest A, Huang D, Nguyen K, Jung ME, Thies RS, Farouz F. Novel oxysterols activate the Hedgehog pathway and induce osteogenesis. Bioorg Med Chem Lett 2012; 22:5893-7. [PMID: 22901899 DOI: 10.1016/j.bmcl.2012.07.073] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 07/16/2012] [Accepted: 07/20/2012] [Indexed: 12/16/2022]
Abstract
Localized induction of bone formation is essential during orthopedic procedures that involve skeletal repair, such as surgical treatment of non-union bone fractures and degenerative disk disease. Herein we disclose the synthesis and biological evaluation of novel oxysterol derivatives designed as anabolic bone growth agents. Structure-activity relationship studies of oxysterol 4 have identified analogues such as 18, 21 and 30. These new analogues are characterized by higher potency in an osteoblast differentiation assay and/or by increased metabolic stability in human liver microsomes. Oxysterols 4, 18 and 21 were evaluated in vivo in a rat spinal fusion model.
Collapse
Affiliation(s)
- Frank Stappenbeck
- Fate Therapeutics, 3535 General Atomics Court, Suite 200, San Diego, CA 92121, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
223
|
Abstract
The Kes1 OSBP (oxysterol-binding protein) is a key regulator of membrane trafficking through the TGN (trans-Golgi network) and endosomal membranes. We demonstrated recently that Kes1 acts as a sterol-regulated rheostat for TGN/endosomal phosphatidylinositol 4-phosphate signalling. Kes1 utilizes its dual lipid-binding activities to integrate endosomal lipid metabolism with TORC1 (target of rapamycin complex 1)-dependent proliferative pathways and transcriptional control of nutrient signalling.
Collapse
|
224
|
Lee S, Wang PY, Jeong Y, Mangelsdorf DJ, Anderson RGW, Michaely P. Sterol-dependent nuclear import of ORP1S promotes LXR regulated trans-activation of apoE. Exp Cell Res 2012; 318:2128-42. [PMID: 22728266 DOI: 10.1016/j.yexcr.2012.06.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 05/30/2012] [Accepted: 06/08/2012] [Indexed: 01/30/2023]
Abstract
Oxysterol binding protein related protein 1S (ORP1S) is a member of a family of sterol transport proteins. Here we present evidence that ORP1S translocates from the cytoplasm to the nucleus in response to sterol binding. The sterols that best promote nuclear import of ORP1S also activate the liver X receptor (LXR) transcription factors and we show that ORP1S binds to LXRs, promotes binding of LXRs to LXR response elements (LXREs) and specifically enhances LXR-dependent transcription via the ME.1 and ME.2 enhancer elements of the apoE gene. We propose that ORP1S is a cytoplasmic sterol sensor, which transports sterols to the nucleus and promotes LXR-dependent gene transcription through select enhancer elements.
Collapse
Affiliation(s)
- Sungsoo Lee
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, United States.
| | | | | | | | | | | |
Collapse
|
225
|
Muller R, Walker S, Brauer J, Junquera M. Does Beer Contain Compounds That Might Interfere with Cholesterol Metabolism? JOURNAL OF THE INSTITUTE OF BREWING 2012. [DOI: 10.1002/j.2050-0416.2007.tb00263.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
226
|
Olkkonen VM, Zhou Y, Yan D, Vihervaara T. Oxysterol-binding proteins-emerging roles in cell regulation. EUR J LIPID SCI TECH 2012. [DOI: 10.1002/ejlt.201200044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
|
227
|
Mousley CJ, Yuan P, Gaur NA, Trettin KD, Nile AH, Deminoff SJ, Dewar BJ, Wolpert M, Macdonald JM, Herman PK, Hinnebusch AG, Bankaitis VA. A sterol-binding protein integrates endosomal lipid metabolism with TOR signaling and nitrogen sensing. Cell 2012; 148:702-15. [PMID: 22341443 DOI: 10.1016/j.cell.2011.12.026] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 10/13/2011] [Accepted: 12/05/2011] [Indexed: 11/18/2022]
Abstract
Kes1, and other oxysterol-binding protein superfamily members, are involved in membrane and lipid trafficking through trans-Golgi network (TGN) and endosomal systems. We demonstrate that Kes1 represents a sterol-regulated antagonist of TGN/endosomal phosphatidylinositol-4-phosphate signaling. This regulation modulates TOR activation by amino acids and dampens gene expression driven by Gcn4, the primary transcriptional activator of the general amino acid control regulon. Kes1-mediated repression of Gcn4 transcription factor activity is characterized by nonproductive Gcn4 binding to its target sequences, involves TGN/endosome-derived sphingolipid signaling, and requires activity of the cyclin-dependent kinase 8 (CDK8) module of the enigmatic "large Mediator" complex. These data describe a pathway by which Kes1 integrates lipid metabolism with TORC1 signaling and nitrogen sensing.
Collapse
Affiliation(s)
- Carl J Mousley
- Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7090, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
228
|
Jacquier N, Schneiter R. Mechanisms of sterol uptake and transport in yeast. J Steroid Biochem Mol Biol 2012; 129:70-8. [PMID: 21145395 DOI: 10.1016/j.jsbmb.2010.11.014] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 11/12/2010] [Accepted: 11/30/2010] [Indexed: 11/21/2022]
Abstract
Sterols are essential lipid components of eukaryotic membranes. Here we summarize recent advances in understanding how sterols are transported between different membranes. Baker's yeast is a particularly attractive organism to dissect this lipid transport pathway, because cells can synthesize their own major sterol, ergosterol, in the membrane of the endoplasmic reticulum from where it is then transported to the plasma membrane. However, Saccharomyces cerevisiae is also a facultative anaerobic organism, which becomes sterol auxotroph in the absence of oxygen. Under these conditions, cells take up sterol from the environment and transport the lipid back into the membrane of the endoplasmic reticulum, where the free sterol becomes esterified and is then stored in lipid droplets. Steryl ester formation is thus a reliable readout to assess the back-transport of exogenously provided sterols from the plasma membrane to the endoplasmic reticulum. Structure/function analysis has revealed that the bulk membrane function of the fungal ergosterol can be provided by structurally related sterols, including the mammalian cholesterol. Foreign sterols, however, are subject to a lipid quality control cycle in which the sterol is reversibly acetylated. Because acetylated sterols are efficiently excreted from cells, the substrate specificity of the deacetylating enzymes determines which sterols are retained. Membrane-bound acetylated sterols are excreted by the secretory pathway, more soluble acetylated sterol derivatives such as the steroid precursor pregnenolone, on the other hand, are excreted by a pathway that is independent of vesicle formation and fusion. Further analysis of this lipid quality control cycle is likely to reveal novel insight into the mechanisms that ensure sterol homeostasis in eukaryotic cells. Article from a special issue on Steroids and Microorganisms.
Collapse
Affiliation(s)
- Nicolas Jacquier
- Department of Medicine, Division of Biochemistry, University of Fribourg, Fribourg, Switzerland
| | | |
Collapse
|
229
|
Beh CT, McMaster CR, Kozminski KG, Menon AK. A detour for yeast oxysterol binding proteins. J Biol Chem 2012; 287:11481-8. [PMID: 22334669 DOI: 10.1074/jbc.r111.338400] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Oxysterol binding protein-related proteins, including the yeast proteins encoded by the OSH gene family (OSH1-OSH7), are implicated in the non-vesicular transfer of sterols between intracellular membranes and the plasma membrane. In light of recent studies, we revisited the proposal that Osh proteins are sterol transfer proteins and present new models consistent with known Osh protein functions. These models focus on the role of Osh proteins as sterol-dependent regulators of phosphoinositide and sphingolipid pathways. In contrast to their posited role as non-vesicular sterol transfer proteins, we propose that Osh proteins coordinate lipid signaling and membrane reorganization with the assembly of tethering complexes to promote molecular exchanges at membrane contact sites.
Collapse
Affiliation(s)
- Christopher T Beh
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
| | | | | | | |
Collapse
|
230
|
Abstract
A new study in this issue (De Saint-Jean et al. 2011. J. Cell Biol.http://dx.doi.org/jcb.201104062) reveals that the sterol transfer protein Osh4p can also transport the signaling phospholipid phosphatidylinositol 4-phosphate (PI(4)P), which binds to the same site in Osh4p as sterol. This finding helps explain some previously published studies and also indicates that lipid/sterol exchange could contribute to establishing a sterol gradient in cells.
Collapse
Affiliation(s)
- Tim P Levine
- Institute of Ophthalmology, University College London, London EC1V 9EL, England, UK.
| |
Collapse
|
231
|
de Saint-Jean M, Delfosse V, Douguet D, Chicanne G, Payrastre B, Bourguet W, Antonny B, Drin G. Osh4p exchanges sterols for phosphatidylinositol 4-phosphate between lipid bilayers. ACTA ACUST UNITED AC 2012; 195:965-78. [PMID: 22162133 PMCID: PMC3241724 DOI: 10.1083/jcb.201104062] [Citation(s) in RCA: 303] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The yeast Kes1p/Osh4p protein functions as a sterol/PI(4)P exchanger between lipid membranes, which suggests the possibility of creating a sterol gradient via phosphoinositide metabolism. Osh/Orp proteins transport sterols between organelles and are involved in phosphoinositide metabolism. The link between these two aspects remains elusive. Using novel assays, we address the influence of membrane composition on the ability of Osh4p/Kes1p to extract, deliver, or transport dehydroergosterol (DHE). Surprisingly, phosphatidylinositol 4-phosphate (PI(4)P) specifically inhibited DHE extraction because PI(4)P was itself efficiently extracted by Osh4p. We solve the structure of the Osh4p–PI(4)P complex and reveal how Osh4p selectively substitutes PI(4)P for sterol. Last, we show that Osh4p quickly exchanges DHE for PI(4)P and, thereby, can transport these two lipids between membranes along opposite routes. These results suggest a model in which Osh4p transports sterol from the ER to late compartments pinpointed by PI(4)P and, in turn, transports PI(4)P backward. Coupled to PI(4)P metabolism, this transport cycle would create sterol gradients. Because the residues that recognize PI(4)P are conserved in Osh4p homologues, other Osh/Orp are potential sterol/phosphoinositol phosphate exchangers.
Collapse
Affiliation(s)
- Maud de Saint-Jean
- Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia-Antipolis and Centre National de la Recherche Scientifique, 06560 Valbonne, France
| | | | | | | | | | | | | | | |
Collapse
|
232
|
Srikantha T, Daniels KJ, Pujol C, Sahni N, Yi S, Soll DR. Nonsex genes in the mating type locus of Candida albicans play roles in a/α biofilm formation, including impermeability and fluconazole resistance. PLoS Pathog 2012; 8:e1002476. [PMID: 22253594 PMCID: PMC3257300 DOI: 10.1371/journal.ppat.1002476] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 11/22/2011] [Indexed: 12/24/2022] Open
Abstract
The mating type locus (MTL) of Candida albicans contains the mating type genes and has, therefore, been assumed to play an exclusive role in the mating process. In mating-incompetent a/α cells, two of the mating type genes, MTLa1 and MTLα2, encode components of the a1-α2 corepressor that suppresses mating and switching. But the MTL locus of C. albicans also contains three apparently unrelated “nonsex” genes (NSGs), PIK, PAP and OBP, the first two essential for growth. Since it had been previously demonstrated that deleting either the a/α copy of the entire MTL locus, or either MTLa1 or MTLα2, affected virulence, we hypothesized that the NSGs in the MTL locus may also play a role in pathogenesis. Here by mutational analysis, it is demonstrated that both the mating type and nonsex genes in the MTL locus play roles in a/α biofilm formation, and that OBP is essential for impermeability and fluconazole resistance. Most natural strains of the yeast pathogen Candida albicans are diploid and heterozygous (a/α) at the mating type locus (MTL). The MTL locus contains mating type genes and has been assumed to play roles exclusively in the mating process of a/a and α/α cells. In C. albicans, however, the MTL locus also contains three nonsex genes (NSGs), the essential phosphatidyl inositol kinase gene, PIK, the essential poly(A) polymerase gene, PAP, and the nonessential oxysterol binding protein gene, OBP. We demonstrate for the first time that both the mating type genes MTLa1 and MTLα2, and the three NSGs play non-mating roles in a/α biofilm formation and virulence. In addition, we show that the NSG OBP is necessary for impermeability and fluconazole resistance of a/α biofilms. These results demonstrate that nonsex genes as well as two mating type genes embedded in the mating type locus, play related roles in pathogenic processes unrelated to mating in a/α cells.
Collapse
Affiliation(s)
- Thyagarajan Srikantha
- The Developmental Studies Hybridoma Bank, Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Karla J. Daniels
- The Developmental Studies Hybridoma Bank, Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Claude Pujol
- The Developmental Studies Hybridoma Bank, Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Nidhi Sahni
- The Developmental Studies Hybridoma Bank, Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Song Yi
- The Developmental Studies Hybridoma Bank, Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - David R. Soll
- The Developmental Studies Hybridoma Bank, Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
| |
Collapse
|
233
|
Membrane phospholipid asymmetry counters the adverse effects of sterol overloading in the Golgi membrane of Drosophila. Genetics 2012; 190:1299-308. [PMID: 22234859 DOI: 10.1534/genetics.111.137687] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Cholesterol and phospholipids serve as structural and functional components of cellular membranes in all eukaryotes. Heterogeneity in cholesterol and phospholipid content both within and between different organelles is an important characteristic of eukaryotic membranes. How this heterogeneity is achieved and orchestrated to maintain proper cellular physiology remains poorly understood. We previously found that overexpression of the Drosophila oxysterol-binding protein (OSBP) leads to sterol accumulation in the Golgi apparatus. Here, we show that Osbp overexpression in a set of neuroendocrine neurons compromises the function of the Golgi apparatus. It impairs trafficking of the neuropeptide bursicon and results in post-eclosion behavior defects characterized by unexpanded wings. We performed a genetic screen to identify modifiers that suppress the unexpanded wing phenotype. A putative phospholipid flippase-encoding gene, CG33298, was validated, suggesting that a membrane-asymmetry-directed mechanism balances cholesterol chaos within the Golgi membranes. Since the functional connection between cholesterol metabolism and the activity of phospholipid flippase has been implicated in studies in yeast and worms, our findings here support an evolutionarily conserved causal link between cholesterol homeostasis and phospholipid asymmetry that maintains normal cellular physiology.
Collapse
|
234
|
Lipid transfer and signaling at organelle contact sites: the tip of the iceberg. Curr Opin Cell Biol 2011; 23:458-63. [PMID: 21555211 DOI: 10.1016/j.ceb.2011.04.006] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Revised: 03/11/2011] [Accepted: 04/18/2011] [Indexed: 01/31/2023]
Abstract
Membrane contact sites (MCSs) are formed by the close apposition of membranes of two organelles. They are zones where signals and small molecules, such as lipids and calcium, are exchanged between intracellular compartments. The past few years have seen considerable progress in our understanding of how MCSs form and facilitate the exchange of lipids and signals. Here we summarize what has been learned about MCSs between the endoplamic reticulum (ER) and the plasma membrane, the ER and mitochondria, and the ER and endosomes or lysosomes. These findings suggest that we are just beginning to understand how MCSs form and function.
Collapse
|
235
|
Abstract
Eukaryotic organelles can interact with each other through stable junctions where the two membranes are kept in close apposition. The junction that connects the endoplasmic reticulum to the plasma membrane (ER-PM junction) is unique in providing a direct communication link between the ER and the PM. In a recently discovered signaling process, STIM (stromal-interacting molecule) proteins sense a drop in ER Ca(2+) levels and directly activate Orai PM Ca(2+) channels across the junction space. In an inverse process, a voltage-gated PM Ca(2+) channel can directly open ER ryanodine-receptor Ca(2+) channels in striated-muscle cells. Although ER-PM junctions were first described 50 years ago, their broad importance in Ca(2+) signaling, as well as in the regulation of cholesterol and phosphatidylinositol lipid transfer, has only recently been realized. Here, we discuss research from different fields to provide a broad perspective on the structures and unique roles of ER-PM junctions in controlling signaling and metabolic processes.
Collapse
Affiliation(s)
- Silvia Carrasco
- Department of Chemical and Systems Biology, School of Medicine, Stanford University, Stanford, California 94305, USA.
| | | |
Collapse
|
236
|
Abstract
Bacteria and eukaryotic cells contain geometry-sensing tools in their cytosol: protein motifs or domains that recognize the curvature, concave or convex, deep or shallow, of lipid membranes. These sensors contrast with classical lipid-binding domains by their extended structure and, sometimes, counterintuitive chemistry. Among the sensors are long amphipathic helices, such as the ALPS motif and the N-terminal region of α-synuclein, whose apparent "design defects" translate into a remarkable ability to specifically adsorb to the surface of small vesicles. Fundamental differences in the lipid composition of membranes of the early and late secretory pathways probably explain why some sensors use mostly electrostatics whereas others take advantage of the hydrophobic effect. Membrane curvature sensors help to organize very diverse reactions, such as lipid transfer between membranes, the tethering of vesicles at the Golgi apparatus, and the assembly-disassembly cycle of protein coats.
Collapse
Affiliation(s)
- Bruno Antonny
- Université de Nice-Sophia Antipolis and Centre National de la Recheche Scientifique, Institut de Pharmacologie Moléculaire et Cellulaire, 06560 Valbonne, France.
| |
Collapse
|
237
|
Elbaz Y, Schuldiner M. Staying in touch: the molecular era of organelle contact sites. Trends Biochem Sci 2011; 36:616-23. [PMID: 21958688 DOI: 10.1016/j.tibs.2011.08.004] [Citation(s) in RCA: 178] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 08/09/2011] [Accepted: 08/15/2011] [Indexed: 01/10/2023]
Abstract
Membrane contact sites (MCS) are close appositions between two organelles that facilitate both signaling and the passage of ions and lipids from one cellular compartment to another. Despite the fact that MCS have been observed for over 50 years now, we still know very little about the molecular machinery required to create them or their structure, function and regulation. In this review, we focus on the three best-characterized contact sites to date: the nucleus-vacuole junction and mitochondria-ER and plasma membrane-ER contact sites. In addition, we discuss principles arising from recent research and highlight several unanswered questions in the field.
Collapse
Affiliation(s)
- Yael Elbaz
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | | |
Collapse
|
238
|
Alfaro G, Johansen J, Dighe SA, Duamel G, Kozminski KG, Beh CT. The Sterol-Binding Protein Kes1/Osh4p Is a Regulator of Polarized Exocytosis. Traffic 2011; 12:1521-36. [DOI: 10.1111/j.1600-0854.2011.01265.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
|
239
|
Vihervaara T, Jansen M, Uronen RL, Ohsaki Y, Ikonen E, Olkkonen VM. Cytoplasmic oxysterol-binding proteins: sterol sensors or transporters? Chem Phys Lipids 2011; 164:443-50. [DOI: 10.1016/j.chemphyslip.2011.03.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Revised: 03/04/2011] [Accepted: 03/04/2011] [Indexed: 12/13/2022]
|
240
|
Fu Q, Lynn-Miller A, Lan Q. Characterization of the oxysterol-binding protein gene family in the yellow fever mosquito, Aedes aegypti. INSECT MOLECULAR BIOLOGY 2011; 20:541-52. [PMID: 21699592 PMCID: PMC3139008 DOI: 10.1111/j.1365-2583.2011.01087.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) are sterol-binding proteins that may be involved in cellular sterol transportation, sterol metabolism and signal transduction pathways. Four ORP genes were cloned from Aedes aegypti. Based on amino acid sequence homology to human proteins, they are AeOSBP, AeORP1, AeORP8 and AeORP9. Splicing variants of AeOSBP and AeORP8 were identified. The temporal and spatial transcription patterns of members of the AeOSBP gene family through developmental stages and the gonotrophic cycle were profiled. AeORP1 transcription seemed to be head tissue-specific, whereas AeOSBP and AeORP9 expression was induced by a bloodmeal. Furthermore, over-expression of AeORPs facilitated [(3)H]-cholesterol uptake in Ae. aegypti cultured Aag -2 cells.
Collapse
Affiliation(s)
- Qiang Fu
- Department of Entomology, University of Wisconsin-Madison, Madison, WI 53705
| | - Ace Lynn-Miller
- Department of Entomology, University of Arkansas, Fayetteville, AR 72701
| | - Que Lan
- Department of Entomology, University of Wisconsin-Madison, Madison, WI 53705
| |
Collapse
|
241
|
Grillitsch K, Connerth M, Köfeler H, Arrey TN, Rietschel B, Wagner B, Karas M, Daum G. Lipid particles/droplets of the yeast Saccharomyces cerevisiae revisited: lipidome meets proteome. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1811:1165-76. [PMID: 21820081 PMCID: PMC3229976 DOI: 10.1016/j.bbalip.2011.07.015] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 07/14/2011] [Accepted: 07/20/2011] [Indexed: 11/28/2022]
Abstract
In the yeast Saccharomyces cerevisiae as in other eukaryotes non-polar lipids are a reservoir of energy and building blocks for membrane lipid synthesis. The yeast non-polar lipids, triacylglycerols (TG) and steryl esters (SE) are stored in so-called lipid particles/droplets (LP) as biologically inert form of fatty acids and sterols. To understand LP structure and function in more detail we investigated the molecular equipment of this compartment making use of mass spectrometric analysis of lipids (TG, SE, phospholipids) and proteins. We addressed the question whether or not lipid and protein composition of LP influence each other and performed analyses of LP from cells grown on two different carbon sources, glucose and oleate. Growth of cells on oleate caused dramatic cellular changes including accumulation of TG at the expense of SE, enhanced the amount of glycerophospholipids and strongly increased the degree of unsaturation in all lipid classes. Most interestingly, oleate as a carbon source led to adaptation of the LP proteome resulting in the appearance of several novel LP proteins. Localization of these new LP proteins was confirmed by cell fractionation. Proteomes of LP variants from cells grown on glucose or oleate, respectively, were compared and are discussed with emphasis on the different groups of proteins detected through this analysis. In summary, we demonstrate flexibility of the yeast LP lipidome and proteome and the ability of LP to adapt to environmental changes.
Collapse
Affiliation(s)
- Karlheinz Grillitsch
- Austrian Centre of Industrial Biotechnology, Graz University of Technology, Austria
| | | | | | | | | | | | | | | |
Collapse
|
242
|
Georgiev AG, Sullivan DP, Kersting MC, Dittman JS, Beh CT, Menon AK. Osh proteins regulate membrane sterol organization but are not required for sterol movement between the ER and PM. Traffic 2011; 12:1341-55. [PMID: 21689253 DOI: 10.1111/j.1600-0854.2011.01234.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Sterol transport between the endoplasmic reticulum (ER) and plasma membrane (PM) occurs by an ATP-dependent, non-vesicular mechanism that is presumed to require sterol transport proteins (STPs). In Saccharomyces cerevisiae, homologs of the mammalian oxysterol-binding protein (Osh1-7) have been proposed to function as STPs. To evaluate this proposal we took two approaches. First we used dehydroergosterol (DHE) to visualize sterol movement in living cells by fluorescence microscopy. DHE was introduced into the PM under hypoxic conditions and observed to redistribute to lipid droplets on growing the cells aerobically. Redistribution required ATP and the sterol acyltransferase Are2, but did not require PM-derived transport vesicles. DHE redistribution occurred robustly in a conditional yeast mutant (oshΔ osh4-1(ts)) that lacks all functional Osh proteins at 37°C. In a second approach we used a pulse-chase protocol to analyze the movement of metabolically radiolabeled ergosterol from the ER to the PM. Arrival of radiolabeled ergosterol at the PM was assessed in isolated PM-enriched fractions as well as by extracting sterols from intact cells with methyl-β-cyclodextrin. These experiments revealed that whereas ergosterol is transported effectively from the ER to the PM in Osh-deficient cells, the rate at which it moves within the PM to equilibrate with the methyl-β-cyclodextrin extractable sterol pool is slowed. We conclude (i) that the role of Osh proteins in non-vesicular sterol transport between the PM, ER and lipid droplets is either minimal, or subsumed by other mechanisms and (ii) that Osh proteins regulate the organization of sterols at the PM.
Collapse
|
243
|
Chrisman CJ, Albuquerque P, Guimaraes AJ, Nieves E, Casadevall A. Phospholipids trigger Cryptococcus neoformans capsular enlargement during interactions with amoebae and macrophages. PLoS Pathog 2011; 7:e1002047. [PMID: 21637814 PMCID: PMC3102711 DOI: 10.1371/journal.ppat.1002047] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Accepted: 03/11/2011] [Indexed: 11/18/2022] Open
Abstract
A remarkable aspect of the interaction of Cryptococcus
neoformans with mammalian hosts is a consistent increase in capsule
volume. Given that many aspects of the interaction of C.
neoformans with macrophages are also observed with amoebae, we
hypothesized that the capsule enlargement phenomenon also had a protozoan
parallel. Incubation of C. neoformans with Acanthamoeba
castellanii resulted in C. neoformans capsular
enlargement. The phenomenon required contact between fungal and protozoan cells
but did not require amoeba viability. Analysis of amoebae extracts showed that
the likely stimuli for capsule enlargement were protozoan polar lipids. Extracts
from macrophages and mammalian serum also triggered cryptococcal capsular
enlargement. C. neoformans capsule enlargement required
expression of fungal phospholipase B, but not phospholipase C. Purified
phospholipids, in particular, phosphatidylcholine, and derived molecules
triggered capsular enlargement with the subsequent formation of giant cells.
These results implicate phospholipids as a trigger for both C.
neoformans capsule enlargement in vivo and
exopolysaccharide production. The observation that the incubation of C.
neoformans with phospholipids led to the formation of giant cells
provides the means to generate these enigmatic cells in vitro.
Protozoan- or mammalian-derived polar lipids could represent a danger signal for
C. neoformans that triggers capsular enlargement as a
non-specific defense mechanism against potential predatory cells. Hence,
phospholipids are the first host-derived molecules identified to trigger
capsular enlargement. The parallels apparent in the capsular response of
C. neoformans to both amoebae and macrophages provide
additional support for the notion that certain aspects of cryptococcal virulence
emerged as a consequence of environmental interactions with other microorganisms
such as protists. A key event in C. neoformans pathogenesis is capsule enlargement
in mammalian hosts. Historically, this phenomenon was attributed to high
CO2 and iron deprivation but the magnitude of capsular
enlargement observed in vivo cannot be consistently replicated
in vitro. This paper reports that C.
neoformans responds to polar lipid extracts with massive capsule
enlargement, with some cells having dimensions comparable to the giant cells
observed in vivo. Phospholipids are identified in this paper as
the inducers of capsule enlargement. Our work is important because this is the
first host-derived molecule that has been identified as a stimulus of massive
capsule enlargement thus providing a potential mechanism for the capsular
enlargement observed in vivo. Furthermore, the fact that the
signal is common to both macrophages and amoebae suggests that the capsule
enlargement response to phospholipids is a mechanism for fungal sensing of
phagocytic cell predators. This provides another example of a correspondence
between a possible environmental signal and a mechanism of virulence.
Collapse
Affiliation(s)
- Cara J. Chrisman
- Department of Microbiology and Immunology,
Albert Einstein College of Medicine, Bronx, New York, United States of
America
| | - Patricia Albuquerque
- Department of Microbiology and Immunology,
Albert Einstein College of Medicine, Bronx, New York, United States of
America
| | - Allan J. Guimaraes
- Department of Microbiology and Immunology,
Albert Einstein College of Medicine, Bronx, New York, United States of
America
| | - Edward Nieves
- Department of Developmental and Molecular
Biology, Albert Einstein College of Medicine, Bronx, New York, United States of
America
- Department of Biochemistry, Albert Einstein
College of Medicine, Bronx, New York, United States of America
| | - Arturo Casadevall
- Department of Microbiology and Immunology,
Albert Einstein College of Medicine, Bronx, New York, United States of
America
- Department of Medicine, Albert Einstein
College of Medicine, Bronx, New York, United States of America
- * E-mail:
| |
Collapse
|
244
|
Du X, Kumar J, Ferguson C, Schulz TA, Ong YS, Hong W, Prinz WA, Parton RG, Brown AJ, Yang H. A role for oxysterol-binding protein-related protein 5 in endosomal cholesterol trafficking. ACTA ACUST UNITED AC 2011; 192:121-35. [PMID: 21220512 PMCID: PMC3019559 DOI: 10.1083/jcb.201004142] [Citation(s) in RCA: 241] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
ORP5 works together with Niemann Pick C-1 to facilitate exit of cholesterol from endosomes and lysosomes. Oxysterol-binding protein (OSBP) and its related proteins (ORPs) constitute a large and evolutionarily conserved family of lipid-binding proteins that target organelle membranes to mediate sterol signaling and/or transport. Here we characterize ORP5, a tail-anchored ORP protein that localizes to the endoplasmic reticulum. Knocking down ORP5 causes cholesterol accumulation in late endosomes and lysosomes, which is reminiscent of the cholesterol trafficking defect in Niemann Pick C (NPC) fibroblasts. Cholesterol appears to accumulate in the limiting membranes of endosomal compartments in ORP5-depleted cells, whereas depletion of NPC1 or both ORP5 and NPC1 results in luminal accumulation of cholesterol. Moreover, trans-Golgi resident proteins mislocalize to endosomal compartments upon ORP5 depletion, which depends on a functional NPC1. Our results establish the first link between NPC1 and a cytoplasmic sterol carrier, and suggest that ORP5 may cooperate with NPC1 to mediate the exit of cholesterol from endosomes/lysosomes.
Collapse
Affiliation(s)
- Ximing Du
- School of Biotechnology and Biomolecular Sciences, the University of New South Wales, Sydney, New South Wales, Australia
| | | | | | | | | | | | | | | | | | | |
Collapse
|
245
|
Stefan CJ, Manford AG, Baird D, Yamada-Hanff J, Mao Y, Emr SD. Osh proteins regulate phosphoinositide metabolism at ER-plasma membrane contact sites. Cell 2011; 144:389-401. [PMID: 21295699 DOI: 10.1016/j.cell.2010.12.034] [Citation(s) in RCA: 368] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 09/17/2010] [Accepted: 12/10/2010] [Indexed: 12/17/2022]
Abstract
Sac1 phosphoinositide (PI) phosphatases are essential regulators of PI-signaling networks. Yeast Sac1, an integral endoplasmic reticulum (ER) membrane protein, controls PI4P levels at the ER, Golgi, and plasma membrane (PM). Whether Sac1 can act in trans and turn over PI4P at the Golgi and PM from the ER remains a paradox. We find that Sac1-mediated PI4P metabolism requires the oxysterol-binding homology (Osh) proteins. The PH domain-containing family member, Osh3, localizes to PM/ER membrane contact sites dependent upon PM PI4P levels. We reconstitute Osh protein-stimulated Sac1 PI phosphatase activity in vitro. We also show that the ER membrane VAP proteins, Scs2/Scs22, control PM PI4P levels and Sac1 activity in vitro. We propose that Osh3 functions at ER/PM contact sites as both a sensor of PM PI4P and an activator of the ER Sac1 phosphatase. Our findings further suggest that the conserved Osh proteins control PI metabolism at additional membrane contact sites.
Collapse
Affiliation(s)
- Christopher J Stefan
- Weill Institute for Cell & Molecular Biology, Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY 14853, USA
| | | | | | | | | | | |
Collapse
|
246
|
Vihervaara T, Uronen RL, Wohlfahrt G, Björkhem I, Ikonen E, Olkkonen VM. Sterol binding by OSBP-related protein 1L regulates late endosome motility and function. Cell Mol Life Sci 2011; 68:537-51. [PMID: 20690035 PMCID: PMC11114714 DOI: 10.1007/s00018-010-0470-z] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 06/24/2010] [Accepted: 07/14/2010] [Indexed: 11/26/2022]
Abstract
ORP1L is an oxysterol binding homologue that regulates late endosome (LE) positioning. We show that ORP1L binds several oxysterols and cholesterol, and characterize a mutant, ORP1L Δ560-563, defective in oxysterol binding. While wild-type ORP1L clusters LE, ORP1L Δ560-563 induces LE scattering, which is reversed by disruption of the endoplasmic reticulum (ER) targeting FFAT motif, suggesting that it is due to enhanced LE-ER interactions. Endosome motility is reduced upon overexpression of ORP1L. Both wild-type ORP1L and the Δ560-563 mutant induce the recruitment of both dynactin and kinesin-2 on LE. Most of the LE decorated by overexpressed ORP1L fail to accept endocytosed dextran or EGF, and the transfected cells display defective degradation of internalized EGF. ORP1L silencing in macrophage foam cells enhances endosome motility and results in inhibition of [(3)H]cholesterol efflux to apolipoprotein A-I. These data demonstrate that LE motility and functions in both protein and lipid transport are regulated by ORP1L.
Collapse
Affiliation(s)
- Terhi Vihervaara
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Tukholmankatu 8, 00290 Helsinki, Finland
- National Institute for Health and Welfare/Public Health Genomics Unit, Biomedicum 1, 00290 Helsinki, Finland
| | - Riikka-Liisa Uronen
- Institute of Biomedicine/Anatomy, University of Helsinki, P.O. Box 63, 00014 Helsinki, Finland
| | - Gerd Wohlfahrt
- Computer-Aided Drug Design, Orion Pharma, Orionintie 1, 02101 Espoo, Finland
| | - Ingemar Björkhem
- Karolinska Institutet, Karolinska University Hospital Huddinge, 14186 Stockholm, Sweden
| | - Elina Ikonen
- Institute of Biomedicine/Anatomy, University of Helsinki, P.O. Box 63, 00014 Helsinki, Finland
| | - Vesa M. Olkkonen
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Tukholmankatu 8, 00290 Helsinki, Finland
- National Institute for Health and Welfare/Public Health Genomics Unit, Biomedicum 1, 00290 Helsinki, Finland
- Institute of Biomedicine/Anatomy, University of Helsinki, P.O. Box 63, 00014 Helsinki, Finland
| |
Collapse
|
247
|
Gimpl G, Gehrig-Burger K. Probes for studying cholesterol binding and cell biology. Steroids 2011; 76:216-31. [PMID: 21074546 DOI: 10.1016/j.steroids.2010.11.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 11/03/2010] [Accepted: 11/05/2010] [Indexed: 11/20/2022]
Abstract
Cholesterol is a multifunctional lipid in eukaryotic cells. It regulates the physical state of the phospholipid bilayer, is crucially involved in the formation of membrane microdomains, affects the activity of many membrane proteins, and is the precursor for steroid hormones and bile acids. Thus, cholesterol plays a profound role in the physiology and pathophysiology of eukaryotic cells. The cholesterol molecule has achieved evolutionary perfection to fulfill its different functions in membrane organization. Here, we review basic approaches to explore the interaction of cholesterol with proteins, with a particular focus on the high diversity of fluorescent and photoreactive cholesterol probes available today.
Collapse
Affiliation(s)
- Gerald Gimpl
- Institute of Pharmacy and Biochemistry, Department of Biochemistry, Johannes Gutenberg-University of Mainz, Mainz, Germany.
| | | |
Collapse
|
248
|
The complex that inserts lipopolysaccharide into the bacterial outer membrane forms a two-protein plug-and-barrel. Proc Natl Acad Sci U S A 2011; 108:2486-91. [PMID: 21257904 DOI: 10.1073/pnas.1015617108] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cell surfaces of Gram-negative bacteria are composed of lipopolysaccharide (LPS). This glycolipid is found exclusively in the outer leaflet of the asymmetric outer membrane (OM), where it forms a barrier to the entry of toxic hydrophobic molecules into the cell. LPS typically contains six fatty acyl chains and up to several hundred sugar residues. It is biosynthesized in the cytosol and must then be transported across two membranes and an aqueous intermembrane space to the cell surface. These processes are required for the viability of most Gram-negative organisms. The integral membrane β-barrel LptD and the lipoprotein LptE form an essential complex in the OM, which is necessary for LPS assembly. It is not known how this complex translocates large, amphipathic LPS molecules across the OM to the outer leaflet. Here, we show that LptE resides within the LptD β-barrel both in vitro and in vivo. LptD/E associate via an extensive interface; in one specific interaction, LptE contacts a predicted extracellular loop of LptD through the lumen of the β-barrel. Disrupting this interaction site compromises the biogenesis of LptD. This unprecedented two-protein plug-and-barrel architecture suggests how LptD/E can insert LPS from the periplasm directly into the outer leaflet of the OM to establish the asymmetry of the bilayer.
Collapse
|
249
|
Jansen M, Ohsaki Y, Rega LR, Bittman R, Olkkonen VM, Ikonen E. Role of ORPs in sterol transport from plasma membrane to ER and lipid droplets in mammalian cells. Traffic 2010; 12:218-31. [PMID: 21062391 DOI: 10.1111/j.1600-0854.2010.01142.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this study, we investigated the mechanisms of sterol transport from the plasma membrane (PM) to the endoplasmic reticulum (ER) and lipid droplets (LDs) in HeLa cells. By overexpressing all mammalian oxysterol-binding protein-related proteins (ORPs), we found that especially ORP1S and ORP2 enhanced PM-to-LD sterol transport. This reflected the stimulation of transport from the PM to the ER, rather than from the ER to LDs. Double knockdown of ORP1S and ORP2 inhibited sterol transport from the PM to the ER and LDs, suggesting a physiological role for these ORPs in the process. A two phenylalanines in an acidic tract (FFAT) motif in ORPs that mediates interaction with VAMP-associated proteins (VAPs) in the ER was not necessary for the enhancement of sterol transport by ORPs. However, VAP-A and VAP-B silencing slowed down PM-to-LD sterol transport. This was accompanied by enhanced degradation of ORP2 and decreased levels of several FFAT motif-containing ORPs, suggesting a role for VAPs in sterol transport by stabilization of ORPs.
Collapse
Affiliation(s)
- Maurice Jansen
- Institute of Biomedicine, University of Helsinki, Finland
| | | | | | | | | | | |
Collapse
|
250
|
Ma Z, Liu Z, Huang X. OSBP- and FAN-mediated sterol requirement for spermatogenesis in Drosophila. Development 2010; 137:3775-84. [DOI: 10.1242/dev.049312] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Members of the oxysterol binding protein (OSBP) family are involved in diverse biological processes, including non-vesicular sterol transport and vesicle trafficking. The mechanisms by which OSBPs integrate functionally with developmental and physiological processes remain elusive. Here, we report the in vivo analysis of OSBP function in the model organism Drosophila. Osbp mutants are male-sterile and exhibit defects in individualization, the process by which each spermatid is packaged into its own membrane. Overexpression of OSBP leads to post-eclosion behaviour defects that can be suppressed by co-expression of endoplasmic reticulum-specific VAP family proteins. Most notably, FAN, a testis-specific VAP protein, acts together with OSBP genetically and physically to regulate the individualization process. OSBP-positive and sterol-enriched speckles are found at the leading edge of the individualization complex in wild type but not in Osbp or fan mutants, suggesting that sterol trafficking might play key roles during the membrane-remodelling phase of individualization. In addition, Osbp mutants that are fed additional sterols partially recover fertility, implying that male sterility is attributable to sterol shortage. Thus, we have identified an OSBP- and FAN-mediated sterol requirement in Drosophila spermatogenesis.
Collapse
Affiliation(s)
- Zhiguo Ma
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhonghua Liu
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Xun Huang
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| |
Collapse
|