1
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Ernst R, Renne MF, Jain A, von der Malsburg A. Endoplasmic Reticulum Membrane Homeostasis and the Unfolded Protein Response. Cold Spring Harb Perspect Biol 2024; 16:a041400. [PMID: 38253414 PMCID: PMC11293554 DOI: 10.1101/cshperspect.a041400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
The endoplasmic reticulum (ER) is the key organelle for membrane biogenesis. Most lipids are synthesized in the ER, and most membrane proteins are first inserted into the ER membrane before they are transported to their target organelle. The composition and properties of the ER membrane must be carefully controlled to provide a suitable environment for the insertion and folding of membrane proteins. The unfolded protein response (UPR) is a powerful signaling pathway that balances protein and lipid production in the ER. Here, we summarize our current knowledge of how aberrant compositions of the ER membrane, referred to as lipid bilayer stress, trigger the UPR.
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Affiliation(s)
- Robert Ernst
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany
- Preclinical Center for Molecular Signaling (PZMS), Medical Faculty, Saarland University, 66421 Homburg, Germany
| | - Mike F Renne
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany
- Preclinical Center for Molecular Signaling (PZMS), Medical Faculty, Saarland University, 66421 Homburg, Germany
| | - Aamna Jain
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany
- Preclinical Center for Molecular Signaling (PZMS), Medical Faculty, Saarland University, 66421 Homburg, Germany
| | - Alexander von der Malsburg
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, 66421 Homburg, Germany
- Preclinical Center for Molecular Signaling (PZMS), Medical Faculty, Saarland University, 66421 Homburg, Germany
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2
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Reinhard J, Starke L, Klose C, Haberkant P, Hammarén H, Stein F, Klein O, Berhorst C, Stumpf H, Sáenz JP, Hub J, Schuldiner M, Ernst R. MemPrep, a new technology for isolating organellar membranes provides fingerprints of lipid bilayer stress. EMBO J 2024; 43:1653-1685. [PMID: 38491296 PMCID: PMC11021466 DOI: 10.1038/s44318-024-00063-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 02/16/2024] [Accepted: 02/26/2024] [Indexed: 03/18/2024] Open
Abstract
Biological membranes have a stunning ability to adapt their composition in response to physiological stress and metabolic challenges. Little is known how such perturbations affect individual organelles in eukaryotic cells. Pioneering work has provided insights into the subcellular distribution of lipids in the yeast Saccharomyces cerevisiae, but the composition of the endoplasmic reticulum (ER) membrane, which also crucially regulates lipid metabolism and the unfolded protein response, remains insufficiently characterized. Here, we describe a method for purifying organelle membranes from yeast, MemPrep. We demonstrate the purity of our ER membrane preparations by proteomics, and document the general utility of MemPrep by isolating vacuolar membranes. Quantitative lipidomics establishes the lipid composition of the ER and the vacuolar membrane. Our findings provide a baseline for studying membrane protein biogenesis and have important implications for understanding the role of lipids in regulating the unfolded protein response (UPR). The combined preparative and analytical MemPrep approach uncovers dynamic remodeling of ER membranes in stressed cells and establishes distinct molecular fingerprints of lipid bilayer stress.
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Affiliation(s)
- John Reinhard
- Saarland University, Medical Biochemistry and Molecular Biology, Homburg, Germany
- Saarland University, Preclinical Center for Molecular Signaling (PZMS), Homburg, Germany
| | - Leonhard Starke
- Saarland University, Theoretical Physics and Center for Biophysics, Saarbrücken, Germany
| | | | - Per Haberkant
- EMBL Heidelberg, Proteomics Core Facility, Heidelberg, Germany
| | | | - Frank Stein
- EMBL Heidelberg, Proteomics Core Facility, Heidelberg, Germany
| | - Ofir Klein
- Weizmann Institute of Science, Department of Molecular Genetics, Rehovot, Israel
| | - Charlotte Berhorst
- Saarland University, Medical Biochemistry and Molecular Biology, Homburg, Germany
- Saarland University, Preclinical Center for Molecular Signaling (PZMS), Homburg, Germany
| | - Heike Stumpf
- Saarland University, Medical Biochemistry and Molecular Biology, Homburg, Germany
- Saarland University, Preclinical Center for Molecular Signaling (PZMS), Homburg, Germany
| | - James P Sáenz
- Technische Universität Dresden, B CUBE, Dresden, Germany
| | - Jochen Hub
- Saarland University, Theoretical Physics and Center for Biophysics, Saarbrücken, Germany
| | - Maya Schuldiner
- Weizmann Institute of Science, Department of Molecular Genetics, Rehovot, Israel
| | - Robert Ernst
- Saarland University, Medical Biochemistry and Molecular Biology, Homburg, Germany.
- Saarland University, Preclinical Center for Molecular Signaling (PZMS), Homburg, Germany.
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3
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Karki S, Javanainen M, Rehan S, Tranter D, Kellosalo J, Huiskonen JT, Happonen L, Paavilainen V. Molecular view of ER membrane remodeling by the Sec61/TRAP translocon. EMBO Rep 2023; 24:e57910. [PMID: 37983950 DOI: 10.15252/embr.202357910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 10/27/2023] [Accepted: 11/01/2023] [Indexed: 11/22/2023] Open
Abstract
Protein translocation across the endoplasmic reticulum (ER) membrane is an essential step during protein entry into the secretory pathway. The conserved Sec61 protein-conducting channel facilitates polypeptide translocation and coordinates cotranslational polypeptide-processing events. In cells, the majority of Sec61 is stably associated with a heterotetrameric membrane protein complex, the translocon-associated protein complex (TRAP), yet the mechanism by which TRAP assists in polypeptide translocation remains unknown. Here, we present the structure of the core Sec61/TRAP complex bound to a mammalian ribosome by cryogenic electron microscopy (cryo-EM). Ribosome interactions anchor the Sec61/TRAP complex in a conformation that renders the ER membrane locally thinner by significantly curving its lumenal leaflet. We propose that TRAP stabilizes the ribosome exit tunnel to assist nascent polypeptide insertion through Sec61 and provides a ratcheting mechanism into the ER lumen mediated by direct polypeptide interactions.
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Affiliation(s)
- Sudeep Karki
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Matti Javanainen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Shahid Rehan
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
- Protein Biochemistry and Structural Biology, Omass Therapeutics Ltd, Oxford, UK
| | - Dale Tranter
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Juho Kellosalo
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Juha T Huiskonen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Lotta Happonen
- Division of Infection Medicine, Department of Clinical Sciences, Lund University, Lund, Sweden
| | - Ville Paavilainen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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4
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Renne MF, Ernst R. Membrane homeostasis beyond fluidity: control of membrane compressibility. Trends Biochem Sci 2023; 48:963-977. [PMID: 37652754 PMCID: PMC10580326 DOI: 10.1016/j.tibs.2023.08.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 08/03/2023] [Accepted: 08/04/2023] [Indexed: 09/02/2023]
Abstract
Biomembranes are complex materials composed of lipids and proteins that compartmentalize biochemistry. They are actively remodeled in response to physical and metabolic cues, as well as during cell differentiation and stress. The concept of homeoviscous adaptation has become a textbook example of membrane responsiveness. Here, we discuss limitations and common misconceptions revolving around it. By highlighting key moments in the life cycle of a transmembrane protein, we illustrate that membrane thickness and a finely regulated membrane compressibility are crucial to facilitate proper membrane protein insertion, function, sorting, and inheritance. We propose that the unfolded protein response (UPR) provides a mechanism for endoplasmic reticulum (ER) membrane homeostasis by sensing aberrant transverse membrane stiffening and triggering adaptive responses that re-establish membrane compressibility.
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Affiliation(s)
- Mike F Renne
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany; PZMS, Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany.
| | - Robert Ernst
- Medical Biochemistry and Molecular Biology, Medical Faculty, Saarland University, Homburg, Germany; PZMS, Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg, Germany.
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Watterson A, Arneaud SLB, Wajahat N, Wall JM, Tatge L, Beheshti ST, Mihelakis M, Cheatwood NY, McClendon J, Ghorashi A, Dehghan I, Corley CD, McDonald JG, Douglas PM. Loss of heat shock factor initiates intracellular lipid surveillance by actin destabilization. Cell Rep 2022; 41:111493. [PMID: 36261024 PMCID: PMC9642076 DOI: 10.1016/j.celrep.2022.111493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 08/19/2022] [Accepted: 09/21/2022] [Indexed: 11/18/2022] Open
Abstract
Cells sense stress and initiate response pathways to maintain lipid and protein homeostasis. However, the interplay between these adaptive mechanisms is unclear. Herein, we demonstrate how imbalances in cytosolic protein homeostasis affect intracellular lipid surveillance. Independent of its ancient thermo-protective properties, the heat shock factor, HSF-1, modulates lipid metabolism and age regulation through the metazoan-specific nuclear hormone receptor, NHR-49. Reduced hsf-1 expression destabilizes the Caenorhabditis elegans enteric actin network, subsequently disrupting Rab GTPase-mediated trafficking and cell-surface residency of nutrient transporters. The ensuing malabsorption limits lipid availability, thereby activating the intracellular lipid surveillance response through vesicular release and nuclear translocation of NHR-49 to both increase nutrient absorption and restore lipid homeostasis. Overall, cooperation between these regulators of cytosolic protein homeostasis and lipid surveillance ensures metabolic health and age progression through actin integrity, endocytic recycling, and lipid sensing.
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Affiliation(s)
- Abigail Watterson
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Sonja L B Arneaud
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Naureen Wajahat
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jordan M Wall
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Lexus Tatge
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Shaghayegh T Beheshti
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Melina Mihelakis
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Nicholas Y Cheatwood
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jacob McClendon
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Atossa Ghorashi
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ishmael Dehghan
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Chase D Corley
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jeffrey G McDonald
- Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Peter M Douglas
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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6
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The Unfolded Protein Response as a Guardian of the Secretory Pathway. Cells 2021; 10:cells10112965. [PMID: 34831188 PMCID: PMC8616143 DOI: 10.3390/cells10112965] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/27/2021] [Accepted: 10/29/2021] [Indexed: 02/07/2023] Open
Abstract
The endoplasmic reticulum (ER) is the major site of membrane biogenesis in most eukaryotic cells. As the entry point to the secretory pathway, it handles more than 10,000 different secretory and membrane proteins. The insertion of proteins into the membrane, their folding, and ER exit are affected by the lipid composition of the ER membrane and its collective membrane stiffness. The ER is also a hotspot of lipid biosynthesis including sterols, glycerophospholipids, ceramides and neural storage lipids. The unfolded protein response (UPR) bears an evolutionary conserved, dual sensitivity to both protein-folding imbalances in the ER lumen and aberrant compositions of the ER membrane, referred to as lipid bilayer stress (LBS). Through transcriptional and non-transcriptional mechanisms, the UPR upregulates the protein folding capacity of the ER and balances the production of proteins and lipids to maintain a functional secretory pathway. In this review, we discuss how UPR transducers sense unfolded proteins and LBS with a particular focus on their role as guardians of the secretory pathway.
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Klein MC, Lerner M, Nguyen D, Pfeffer S, Dudek J, Förster F, Helms V, Lang S, Zimmermann R. TRAM1 protein may support ER protein import by modulating the phospholipid bilayer near the lateral gate of the Sec61-channel. Channels (Austin) 2021; 14:28-44. [PMID: 32013668 PMCID: PMC7039644 DOI: 10.1080/19336950.2020.1724759] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
In mammalian cells, one-third of all polypeptides is transported into or through the ER-membrane via the Sec61-channel. While the Sec61-complex facilitates the transport of all polypeptides with amino-terminal signal peptides (SP) or SP-equivalent transmembrane helices (TMH), the translocating chain-associated membrane protein (now termed TRAM1) was proposed to support transport of a subset of precursors. To identify possible determinants of TRAM1 substrate specificity, we systematically identified TRAM1-dependent precursors by analyzing cellular protein abundance changes upon TRAM1 depletion in HeLa cells using quantitative label-free proteomics. In contrast to previous analysis after TRAP depletion, SP and TMH analysis of TRAM1 clients did not reveal any distinguishing features that could explain its putative substrate specificity. To further address the TRAM1 mechanism, live-cell calcium imaging was carried out after TRAM1 depletion in HeLa cells. In additional contrast to previous analysis after TRAP depletion, TRAM1 depletion did not affect calcium leakage from the ER. Thus, TRAM1 does not appear to act as SP- or TMH-receptor on the ER-membrane’s cytosolic face and does not appear to affect the open probability of the Sec61-channel. It may rather play a supportive role in protein transport, such as making the phospholipid bilayer conducive for accepting SP and TMH in the vicinity of the lateral gate of the Sec61-channel. Abbreviations: ER, endoplasmic reticulum; OST, oligosaccharyltransferase; RAMP, ribosome-associated membrane protein; SP, signal peptide; SR, SRP-receptor; SRP, signal recognition particle; TMH, signal peptide-equivalent transmembrane helix; TRAM, translocating chain-associated membrane protein; TRAP, translocon-associated protein.
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Affiliation(s)
| | - Monika Lerner
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Duy Nguyen
- Center for Bioinformatics, Saarland University, Saarbrücken, Germany
| | | | - Johanna Dudek
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Friedrich Förster
- Bijvoet Center for Biomolecular Research, Utrecht University, Utrecht, The Netherlands
| | - Volkhard Helms
- Center for Bioinformatics, Saarland University, Saarbrücken, Germany
| | - Sven Lang
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Richard Zimmermann
- Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
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8
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Vandebrouck C, Ferreira T. Glued in lipids: Lipointoxication in cystic fibrosis. EBioMedicine 2020; 61:103038. [PMID: 33038767 PMCID: PMC7648119 DOI: 10.1016/j.ebiom.2020.103038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/27/2020] [Accepted: 09/14/2020] [Indexed: 01/14/2023] Open
Abstract
Cystic Fibrosis (CF) is an autosomal recessive disease caused by mutations in the CF transmembrane regulator (CFTR) gene, which encodes a chloride channel located at the apical surface of epithelial cells. Unsaturated Fatty Acid (UFA) deficiency has been a persistent observation in tissues from patients with CF. However, the impacts of such deficiencies on the etiology of the disease have been the object of intense debates. The aim of the present review is first to highlight the general consensus on fatty acid dysregulations that emerges from, sometimes apparently contradictory, studies. In a second step, a unifying mechanism for the potential impacts of these fatty acid dysregulations in CF cells, based on alterations of membrane biophysical properties (known as lipointoxication), is proposed. Finally, the contribution of lipointoxication to the progression of the CF disease and how it could affect the efficacy of current treatments is also discussed.
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Affiliation(s)
- Clarisse Vandebrouck
- Laboratoire "Lipointoxication and Channelopathies (LiTch) - ConicMeds", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France; Laboratoire "Signalisation et Transports Ioniques Membranaires (STIM; EA 7349)", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France
| | - Thierry Ferreira
- Laboratoire "Lipointoxication and Channelopathies (LiTch) - ConicMeds", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France.
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9
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Covino R, Hummer G, Ernst R. Integrated Functions of Membrane Property Sensors and a Hidden Side of the Unfolded Protein Response. Mol Cell 2019; 71:458-467. [PMID: 30075144 DOI: 10.1016/j.molcel.2018.07.019] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/09/2018] [Accepted: 07/17/2018] [Indexed: 12/26/2022]
Abstract
Eukaryotic cells face the challenge of maintaining the complex composition of several coexisting organelles. The molecular mechanisms underlying the homeostasis of subcellular membranes and their adaptation during stress are only now starting to emerge. Here, we discuss three membrane property sensors of the endoplasmic reticulum (ER), namely OPI1, MGA2, and IRE1, each controlling a large cellular program impacting the lipid metabolic network. OPI1 coordinates the production of membrane and storage lipids, MGA2 regulates the production of unsaturated fatty acids required for membrane biogenesis, and IRE1 controls the unfolded protein response (UPR) to adjust ER size, protein folding, and the secretory capacity of the cell. Although these proteins use remarkably distinct sensing mechanisms, they are functionally connected via the ER membrane and cooperate to maintain membrane homeostasis. As a rationalization of the recently described mechanism of UPR activation by lipid bilayer stress, we propose that IRE1 can sense the protein-to-lipid ratio in the ER membrane to ensure a balanced production of membrane proteins and lipids.
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Affiliation(s)
- Roberto Covino
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany; Institute of Biophysics, Goethe University, 60438 Frankfurt am Main, Germany
| | - Robert Ernst
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Kirrberger Str. 100, Gebäude 61.4, 66421 Homburg, Germany.
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10
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Sørensen DM, Holen HW, Pedersen JT, Martens HJ, Silvestro D, Stanchev LD, Costa SR, Günther Pomorski T, López-Marqués RL, Palmgren M. The P5A ATPase Spf1p is stimulated by phosphatidylinositol 4-phosphate and influences cellular sterol homeostasis. Mol Biol Cell 2019; 30:1069-1084. [PMID: 30785834 PMCID: PMC6724510 DOI: 10.1091/mbc.e18-06-0365] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
P5A ATPases are expressed in the endoplasmic reticulum (ER) of all eukaryotic cells, and their disruption results in severe ER stress. However, the function of these ubiquitous membrane proteins, which belong to the P-type ATPase superfamily, is unknown. We purified a functional tagged version of the Saccharomyces cerevisiae P5A ATPase Spf1p and observed that the ATP hydrolytic activity of the protein is stimulated by phosphatidylinositol 4-phosphate (PI4P). Furthermore, SPF1 exhibited negative genetic interactions with SAC1, encoding a PI4P phosphatase, and with OSH1 to OSH6, encoding Osh proteins, which, when energized by a PI4P gradient, drive export of sterols and lipids from the ER. Deletion of SPF1 resulted in increased sensitivity to inhibitors of sterol production, a marked change in the ergosterol/lanosterol ratio, accumulation of sterols in the plasma membrane, and cytosolic accumulation of lipid bodies. We propose that Spf1p maintains cellular sterol homeostasis by influencing the PI4P-induced and Osh-mediated export of sterols from the ER.
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Affiliation(s)
- Danny Mollerup Sørensen
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
| | - Henrik Waldal Holen
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
| | - Jesper Torbøl Pedersen
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
| | - Helle Juel Martens
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
| | - Daniele Silvestro
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
| | - Lyubomir Dimitrov Stanchev
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
| | - Sara Rute Costa
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
| | - Thomas Günther Pomorski
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
| | - Rosa Laura López-Marqués
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
| | - Michael Palmgren
- Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
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11
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Pichler H, Emmerstorfer-Augustin A. Modification of membrane lipid compositions in single-celled organisms – From basics to applications. Methods 2018; 147:50-65. [DOI: 10.1016/j.ymeth.2018.06.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 05/18/2018] [Accepted: 06/16/2018] [Indexed: 12/12/2022] Open
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12
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Kadri L, Ferru-Clément R, Bacle A, Payet LA, Cantereau A, Hélye R, Becq F, Jayle C, Vandebrouck C, Ferreira T. Modulation of cellular membrane properties as a potential therapeutic strategy to counter lipointoxication in obstructive pulmonary diseases. Biochim Biophys Acta Mol Basis Dis 2018; 1864:3069-3084. [PMID: 29960042 DOI: 10.1016/j.bbadis.2018.06.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 06/04/2018] [Accepted: 06/25/2018] [Indexed: 02/08/2023]
Abstract
Maintaining the equilibrium between saturated and unsaturated fatty acids within membrane phospholipids (PLs) is crucial to sustain the optimal membrane biophysical properties, compatible with selective organelle-based processes. Lipointoxication is a pathological condition under which saturated PLs tend to accumulate within the cell at the expense of unsaturated species, with major impacts on organelle function. Here, we show that human bronchial epithelial cells extracted from lungs of patients with Obstructive Pulmonary Diseases (OPDs), i. e. Cystic Fibrosis (CF) individuals and Smokers, display a characteristic lipointoxication signature, with excessive amounts of saturated PLs. Reconstitution of this signature in cellulo and in silico revealed that such an imbalance results in altered membrane properties and in a dramatic disorganization of the intracellular network of bronchial epithelial cells, in a process which can account for several OPD traits. Such features include Endoplasmic Reticulum-stress, constitutive IL8 secretion, bronchoconstriction and, ultimately, epithelial cell death by apoptosis. We also demonstrate that a recently-identified lipid-like molecule, which has been shown to behave as a "membrane-reshaper", counters all the lipointoxication hallmarks tested. Altogether, these insights highlight the modulation of membrane properties as a potential new strategy to heal and prevent highly detrimental symptoms associated with OPDs.
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Affiliation(s)
- Linette Kadri
- Laboratoire Coopératif "Lipotoxicity and Channelopathies - ConicMeds", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France
| | - Romain Ferru-Clément
- Laboratoire Coopératif "Lipotoxicity and Channelopathies - ConicMeds", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France
| | - Amélie Bacle
- Laboratoire Coopératif "Lipotoxicity and Channelopathies - ConicMeds", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France
| | - Laurie-Anne Payet
- Laboratoire "Signalisation et Transports Ioniques Membranaires (STIM)", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France
| | - Anne Cantereau
- Laboratoire "Signalisation et Transports Ioniques Membranaires (STIM)", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France
| | - Reynald Hélye
- Laboratoire Coopératif "Lipotoxicity and Channelopathies - ConicMeds", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France
| | - Frédéric Becq
- Laboratoire "Signalisation et Transports Ioniques Membranaires (STIM)", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France
| | - Christophe Jayle
- Service de Chirurgie Cardiothoracique, CHU Poitiers, Poitiers, France
| | - Clarisse Vandebrouck
- Laboratoire "Signalisation et Transports Ioniques Membranaires (STIM)", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France
| | - Thierry Ferreira
- Laboratoire Coopératif "Lipotoxicity and Channelopathies - ConicMeds", Université de Poitiers, 1, rue Georges Bonnet, Poitiers, France.
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13
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Radanović T, Reinhard J, Ballweg S, Pesek K, Ernst R. An Emerging Group of Membrane Property Sensors Controls the Physical State of Organellar Membranes to Maintain Their Identity. Bioessays 2018; 40:e1700250. [PMID: 29574931 DOI: 10.1002/bies.201700250] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Revised: 02/06/2018] [Indexed: 11/06/2022]
Abstract
The biological membranes of eukaryotic cells harbor sensitive surveillance systems to establish, sense, and maintain characteristic physicochemical properties that ultimately define organelle identity. They are fundamentally important for membrane homeostasis and play active roles in cellular signaling, protein sorting, and the formation of vesicular carriers. Here, we compare the molecular mechanisms of Mga2 and Ire1, two sensors involved in the regulation of fatty acid desaturation and the response to unfolded proteins and lipid bilayer stress in order to identify their commonalities and specializations. We will speculate on the cellular significance of membrane property sensors in other organelles and discuss their putative mechanisms. Based on these findings, we propose membrane property sensors as an emerging class of proteins with wide implications for organelle communication and function.
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Affiliation(s)
- Toni Radanović
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
| | - John Reinhard
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
| | - Stephanie Ballweg
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
| | - Kristina Pesek
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
| | - Robert Ernst
- Medical Faculty, Department of Medical Biochemistry and Molecular Bioloy, Saarland University, 66421 Homburg, Germany
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14
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Hussain SS, Harris MT, Kreutzberger AJB, Inouye CM, Doyle CA, Castle AM, Arvan P, Castle JD. Control of insulin granule formation and function by the ABC transporters ABCG1 and ABCA1 and by oxysterol binding protein OSBP. Mol Biol Cell 2018. [PMID: 29540530 PMCID: PMC5935073 DOI: 10.1091/mbc.e17-08-0519] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In pancreatic β-cells, insulin granule membranes are enriched in cholesterol and are both recycled and newly generated. Cholesterol’s role in supporting granule membrane formation and function is poorly understood. ATP binding cassette transporters ABCG1 and ABCA1 regulate intracellular cholesterol and are important for insulin secretion. RNAi interference–induced depletion in cultured pancreatic β-cells shows that ABCG1 is needed to stabilize newly made insulin granules against lysosomal degradation; ABCA1 is also involved but to a lesser extent. Both transporters are also required for optimum glucose-stimulated insulin secretion, likely via complementary roles. Exogenous cholesterol addition rescues knockdown-induced granule loss (ABCG1) and reduced secretion (both transporters). Another cholesterol transport protein, oxysterol binding protein (OSBP), appears to act proximally as a source of endogenous cholesterol for granule formation. Its knockdown caused similar defective stability of young granules and glucose-stimulated insulin secretion, neither of which were rescued with exogenous cholesterol. Dual knockdowns of OSBP and ABC transporters support their serial function in supplying and concentrating cholesterol for granule formation. OSBP knockdown also decreased proinsulin synthesis consistent with a proximal endoplasmic reticulum defect. Thus, membrane cholesterol distribution contributes to insulin homeostasis at production, packaging, and export levels through the actions of OSBP and ABCs G1 and A1.
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Affiliation(s)
- Syed Saad Hussain
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Megan T Harris
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Alex J B Kreutzberger
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908.,Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Candice M Inouye
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Catherine A Doyle
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Anna M Castle
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Peter Arvan
- Division of Metabolism, Endocrinology, and Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105
| | - J David Castle
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908.,Center for Membrane and Cell Physiology, University of Virginia School of Medicine, Charlottesville, VA 22908
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15
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Renne MF, de Kroon AIPM. The role of phospholipid molecular species in determining the physical properties of yeast membranes. FEBS Lett 2017; 592:1330-1345. [PMID: 29265372 PMCID: PMC5947837 DOI: 10.1002/1873-3468.12944] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 11/27/2017] [Accepted: 12/11/2017] [Indexed: 12/18/2022]
Abstract
In most eukaryotes, including Saccharomyces cerevisiae, glycerophospholipids are the main membrane lipid constituents. Besides serving as general membrane ‘building blocks’, glycerophospholipids play an important role in determining the physical properties of the membrane, which are crucial for proper membrane function. To ensure optimal physical properties, membrane glycerophospholipid composition and synthesis are tightly regulated. This review will summarize our current knowledge of factors and processes determining the membrane glycerophospholipid composition of the reference eukaryote S. cerevisiae at the level of molecular species. Extrapolating from relevant model membrane data, we also discuss how modulation of the molecular species composition can regulate membrane physical properties.
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Affiliation(s)
- Mike F. Renne
- Membrane Biochemistry & BiophysicsDepartment of ChemistryBijvoet Center for Biomolecular Research & Institute of BiomembranesUtrecht Universitythe Netherlands
| | - Anton I. P. M. de Kroon
- Membrane Biochemistry & BiophysicsDepartment of ChemistryBijvoet Center for Biomolecular Research & Institute of BiomembranesUtrecht Universitythe Netherlands
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16
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Jain A, Holthuis JCM. Membrane contact sites, ancient and central hubs of cellular lipid logistics. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1864:1450-1458. [PMID: 28554771 DOI: 10.1016/j.bbamcr.2017.05.017] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 05/10/2017] [Accepted: 05/17/2017] [Indexed: 12/26/2022]
Abstract
Membrane contact sites (MCSs) are regions where two organelles are closely apposed to facilitate molecular communication and promote a functional integration of compartmentalized cellular processes. There is growing evidence that MCSs play key roles in controlling intracellular lipid flows and distributions. Strikingly, even organelles connected by vesicular trafficking exchange lipids en bulk via lipid transfer proteins that operate at MCSs. Herein, we describe how MCSs developed into central hubs of lipid logistics during the evolution of eukaryotic cells. We then focus on how modern eukaryotes exploit MCSs to help solve a major logistical problem, namely to preserve the unique lipid mixtures of their early and late secretory organelles in the face of extensive vesicular trafficking. This article is part of a Special Issue entitled: Membrane Contact Sites edited by Christian Ungermann and Benoit Kornmann.
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Affiliation(s)
- Amrita Jain
- Molecular Cell Biology Division, Department of Biology/Chemistry, University of Osnabrück, D-49076 Osnabrück, Germany
| | - Joost C M Holthuis
- Molecular Cell Biology Division, Department of Biology/Chemistry, University of Osnabrück, D-49076 Osnabrück, Germany; Membrane Biochemistry & Biophysics, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands.
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17
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Vitrac H, MacLean DM, Karlstaedt A, Taegtmeyer H, Jayaraman V, Bogdanov M, Dowhan W. Dynamic Lipid-dependent Modulation of Protein Topology by Post-translational Phosphorylation. J Biol Chem 2016; 292:1613-1624. [PMID: 27974465 DOI: 10.1074/jbc.m116.765719] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/13/2016] [Indexed: 01/01/2023] Open
Abstract
Membrane protein topology and folding are governed by structural principles and topogenic signals that are recognized and decoded by the protein insertion and translocation machineries at the time of initial membrane insertion and folding. We previously demonstrated that the lipid environment is also a determinant of initial protein topology, which is dynamically responsive to post-assembly changes in membrane lipid composition. However, the effect on protein topology of post-assembly phosphorylation of amino acids localized within initially cytoplasmically oriented extramembrane domains has never been investigated. Here, we show in a controlled in vitro system that phosphorylation of a membrane protein can trigger a change in topological arrangement. The rate of change occurred on a scale of seconds, comparable with the rates observed upon changes in the protein lipid environment. The rate and extent of topological rearrangement were dependent on the charges of extramembrane domains and the lipid bilayer surface. Using model membranes mimicking the lipid compositions of eukaryotic organelles, we determined that anionic lipids, cholesterol, sphingomyelin, and membrane fluidity play critical roles in these processes. Our results demonstrate how post-translational modifications may influence membrane protein topology in a lipid-dependent manner, both along the organelle trafficking pathway and at their final destination. The results provide further evidence that membrane protein topology is dynamic, integrating for the first time the effect of changes in lipid composition and regulators of cellular processes. The discovery of a new topology regulatory mechanism opens additional avenues for understanding unexplored structure-function relationships and the development of optimized topology prediction tools.
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Affiliation(s)
- Heidi Vitrac
- From the Department of Biochemistry and Molecular Biology and Center for Membrane Biology, University of Texas McGovern Medical School, Houston, Texas 77030.
| | - David M MacLean
- From the Department of Biochemistry and Molecular Biology and Center for Membrane Biology, University of Texas McGovern Medical School, Houston, Texas 77030
| | - Anja Karlstaedt
- the Department of Internal Medicine, Division of Cardiology, University of Texas McGovern Medical School, Houston, Texas 77030
| | - Heinrich Taegtmeyer
- the Department of Internal Medicine, Division of Cardiology, University of Texas McGovern Medical School, Houston, Texas 77030
| | - Vasanthi Jayaraman
- From the Department of Biochemistry and Molecular Biology and Center for Membrane Biology, University of Texas McGovern Medical School, Houston, Texas 77030
| | - Mikhail Bogdanov
- From the Department of Biochemistry and Molecular Biology and Center for Membrane Biology, University of Texas McGovern Medical School, Houston, Texas 77030
| | - William Dowhan
- From the Department of Biochemistry and Molecular Biology and Center for Membrane Biology, University of Texas McGovern Medical School, Houston, Texas 77030.
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18
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The counterflow transport of sterols and PI4P. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:940-951. [PMID: 26928592 DOI: 10.1016/j.bbalip.2016.02.024] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 02/23/2016] [Accepted: 02/24/2016] [Indexed: 02/03/2023]
Abstract
Cholesterol levels in intracellular membranes are constantly adjusted to match with specific organelle functions. Cholesterol is kept high in the plasma membrane (PM) because it is essential for its barrier function, while low levels are found in the endoplasmic reticulum (ER) where cholesterol mediates feedback control of its own synthesis by sterol-sensor proteins. The ER→Golgi→PM concentration gradient of cholesterol in mammalian cells, and ergosterol in yeast, appears to be sustained by specific intracellular transport processes, which are mostly mediated by lipid transfer proteins (LTPs). Here we review a recently described function of two LTPs, OSBP and its yeast homolog Osh4p, which consists in creating a sterol gradient between membranes by vectorial transport. OSBP also contributes to the formation of ER/Golgi membrane contact sites, which are important hubs for the transfer of several lipid species. OSBP and Osh4p organize a counterflow transport of lipids whereby sterols are exchanged for the phosphoinositide PI4P, which is used as a fuel to drive sterol transport. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon.
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19
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Simons K. Cell membranes: A subjective perspective. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2569-2572. [PMID: 26827711 DOI: 10.1016/j.bbamem.2016.01.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 01/19/2016] [Accepted: 01/21/2016] [Indexed: 11/29/2022]
Abstract
Cell membranes have developed a tremendous complexity of lipids and proteins geared to perform the functions cells require. The lipids have for long remained in the background and are now regaining their role as important building blocks of cells. Their main function is to form the matrix of our cell membranes where they support a variety of functions essential for life. This 2-dimensional fluid matrix has evolved unexpected material properties that involve both lipid-lipid and lipid-protein interactions. This perspective is a short summary of the challenges that this field faces and discusses potential ways and means for coming to grips with the properties of this incredible fluid. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.
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Affiliation(s)
- Kai Simons
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.
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20
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Hernández A, Serrano-Bueno G, Perez-Castiñeira JR, Serrano A. 8-Dehydrosterols induce membrane traffic and autophagy defects through V-ATPase dysfunction in Saccharomyces cerevisae. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2945-56. [PMID: 26344037 DOI: 10.1016/j.bbamcr.2015.09.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 09/01/2015] [Indexed: 12/11/2022]
Abstract
8-Dehydrosterols are present in a wide range of biologically relevant situations, from human rare diseases to amine fungicide-treated fungi and crops. However, the molecular bases of their toxicity are still obscure. We show here that 8-dehydrosterols, but not other sterols, affect yeast vacuole acidification through V-ATPases. Moreover, erg2Δ cells display reductions in proton pumping rates consistent with ion-transport uncoupling in vitro. Concomitantly, subunit Vph1p shows conformational changes in the presence of 8-dehydrosterols. Expression of a plant vacuolar H(+)-pumping pyrophosphatase as an alternative H(+)-pump relieves Vma(-)-like phenotypes in erg2Δ-derived mutant cells. As a consequence of these acidification defects, endo- and exo-cytic traffic deficiencies that can be alleviated with a H(+)-pumping pyrophosphatase are also observed. Despite their effect on membrane traffic, 8-dehydrosterols do not induce endoplasmic reticulum stress or assembly defects on the V-ATPase. Autophagy is a V-ATPase dependent process and erg2Δ mutants accumulate autophagic bodies under nitrogen starvation similar to Vma(-) mutants. In contrast to classical Atg(-) mutants, this defect is not accompanied by impairment of traffic through the CVT pathway, processing of Pho8Δ60p, GFP-Atg8p localisation or difficulties to survive under nitrogen starvation conditions, but it is concomitant to reduced vacuolar protease activity. All in all, erg2Δ cells are autophagy mutants albeit some of their phenotypic features differ from classical Atg(-) defective cells. These results may pave the way to understand the aetiology of sterol-related diseases, the cytotoxic effect of amine fungicides, and may explain the tolerance to these compounds observed in plants.
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Affiliation(s)
- Agustín Hernández
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda Américo Vespucio 48, 41092 Sevilla, Spain.
| | - Gloria Serrano-Bueno
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda Américo Vespucio 48, 41092 Sevilla, Spain
| | - José Román Perez-Castiñeira
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda Américo Vespucio 48, 41092 Sevilla, Spain
| | - Aurelio Serrano
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda Américo Vespucio 48, 41092 Sevilla, Spain.
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21
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Kalies KU, Römisch K. Inhibitors of Protein Translocation Across the ER Membrane. Traffic 2015; 16:1027-38. [PMID: 26122014 DOI: 10.1111/tra.12308] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 06/18/2015] [Accepted: 06/22/2015] [Indexed: 12/21/2022]
Abstract
Protein translocation into the endoplasmic reticulum (ER) constitutes the first step of protein secretion. ER protein import is essential in all eukaryotic cells and is particularly critical in fast-growing tumour cells. Thus, the process can serve as target both for potential cancer drugs and for bacterial virulence factors. Inhibitors of protein transport across the ER membrane range from broad-spectrum to highly substrate-specific and can interfere with virtually any stage of this multistep process, and even with transport of endocytosed antigens into the cytosol for cross-presentation.
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Affiliation(s)
- Kai-Uwe Kalies
- Institute of Biology, CSCM, University of Lübeck, Lübeck, Germany
| | - Karin Römisch
- Department of Microbiology, Faculty of Natural Sciences and Technology VIII, Saarland University, 66123, Saarbrücken, Germany
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22
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Antonny B, Vanni S, Shindou H, Ferreira T. From zero to six double bonds: phospholipid unsaturation and organelle function. Trends Cell Biol 2015; 25:427-36. [DOI: 10.1016/j.tcb.2015.03.004] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 03/19/2015] [Accepted: 03/23/2015] [Indexed: 01/21/2023]
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23
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Lipid landscapes and pipelines in membrane homeostasis. Nature 2014; 510:48-57. [DOI: 10.1038/nature13474] [Citation(s) in RCA: 743] [Impact Index Per Article: 74.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Accepted: 04/03/2014] [Indexed: 11/08/2022]
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24
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Denks K, Vogt A, Sachelaru I, Petriman NA, Kudva R, Koch HG. The Sec translocon mediated protein transport in prokaryotes and eukaryotes. Mol Membr Biol 2014; 31:58-84. [DOI: 10.3109/09687688.2014.907455] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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25
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Maurel M, Chevet E, Tavernier J, Gerlo S. Getting RIDD of RNA: IRE1 in cell fate regulation. Trends Biochem Sci 2014; 39:245-54. [PMID: 24657016 DOI: 10.1016/j.tibs.2014.02.008] [Citation(s) in RCA: 427] [Impact Index Per Article: 42.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 02/20/2014] [Accepted: 02/21/2014] [Indexed: 12/12/2022]
Abstract
Inositol-requiring enzyme 1 (IRE1) is the most conserved transducer of the unfolded protein response (UPR), a homeostatic response that preserves proteostasis. Intriguingly, via its endoribonuclease activity, IRE1 produces either adaptive or death signals. This occurs through both unconventional splicing of XBP1 mRNA and regulated IRE1-dependent decay of mRNA (RIDD). Whereas XBP1 mRNA splicing is cytoprotective in response to endoplasmic reticulum (ER) stress, RIDD has revealed many unexpected features. For instance, RIDD cleaves RNA at an XBP1-like consensus site but with an activity divergent from XBP1 mRNA splicing and can either preserve ER homeostasis or induce cell death. Here we review recent findings on RIDD and propose a model of how IRE1 RNase activity might control cell fate decisions.
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Affiliation(s)
- M Maurel
- Department of Medical Protein Research, VIB, Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
| | - E Chevet
- INSERM U1053, Université Bordeaux Segalen, 33000 Bordeaux, France; Centre Régional de Lutte Contre le Cancer Eugène Marquis, 35000 Rennes, France
| | - J Tavernier
- Department of Medical Protein Research, VIB, Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - S Gerlo
- Department of Medical Protein Research, VIB, Ghent, Belgium; Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
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26
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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.
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Affiliation(s)
- Joëlle Bigay
- Institut de Pharmacologie Moléculaire et Cellulaire, Université de Nice Sophia Antipolis et CNRS, 06560 Valbonne, France
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27
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Kimmig P, Diaz M, Zheng J, Williams CC, Lang A, Aragón T, Li H, Walter P. The unfolded protein response in fission yeast modulates stability of select mRNAs to maintain protein homeostasis. eLife 2012; 1:e00048. [PMID: 23066505 PMCID: PMC3470409 DOI: 10.7554/elife.00048] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 07/23/2012] [Indexed: 01/19/2023] Open
Abstract
The unfolded protein response (UPR) monitors the protein folding capacity of the endoplasmic reticulum (ER). In all organisms analyzed to date, the UPR drives transcriptional programs that allow cells to cope with ER stress. The non-conventional splicing of Hac1 (yeasts) and XBP1 (metazoans) mRNA, encoding orthologous UPR transcription activators, is conserved and dependent on Ire1, an ER membrane-resident kinase/endoribonuclease. We found that the fission yeast Schizosaccharomyces pombe lacks both a Hac1/XBP1 ortholog and a UPR-dependent-transcriptional-program. Instead, Ire1 initiates the selective decay of a subset of ER-localized-mRNAs that is required to survive ER stress. We identified Bip1 mRNA, encoding a major ER-chaperone, as the sole mRNA cleaved upon Ire1 activation that escapes decay. Instead, truncation of its 3' UTR, including loss of its polyA tail, stabilized Bip1 mRNA, resulting in increased Bip1 translation. Thus, S. pombe uses a universally conserved stress-sensing machinery in novel ways to maintain homeostasis in the ER.DOI:http://dx.doi.org/10.7554/eLife.00048.001.
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Affiliation(s)
- Philipp Kimmig
- Department of Biochemistry and Biophysics , University of California, San Francisco , San Francisco , United States
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28
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Yamamoto H, Fujita H, Kida Y, Sakaguchi M. Pleiotropic effects of membrane cholesterol upon translocation of protein across the endoplasmic reticulum membrane. Biochemistry 2012; 51:3596-605. [PMID: 22493992 DOI: 10.1021/bi2018915] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Various proteins are translocated through and inserted into the endoplasmic reticulum membrane via translocon channels. The hydrophobic segments of signal sequences initiate translocation, and those on translocating polypeptides interrupt translocation to be inserted into the membrane. Positive charges suppress translocation to regulate the orientation of the signal sequences. Here, we investigated the effect of membrane cholesterol on the translocational behavior of nascent chains in a cell-free system. We found that the three distinct translocation processes were sensitive to membrane cholesterol. Cholesterol inhibited the initiation of translocation by the signal sequence, and the extent of inhibition depended on the signal sequence. Even when initiation was not inhibited, cholesterol impeded the movement of the positively charged residues of the translocating polypeptide chain. In surprising contrast, cholesterol enhanced the translocation of hydrophobic sequences through the translocon. On the basis of these findings, we propose that membrane cholesterol greatly affects partitioning of hydrophobic segments into the membrane and impedes the movement of positive charges.
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Affiliation(s)
- Hitoshi Yamamoto
- Graduate School of Life Science, University of Hyogo, Kouto 3-2-1, Ako-gun, Hyogo 678-1297, Japan
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29
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Coskun U, Simons K. Cell membranes: the lipid perspective. Structure 2012; 19:1543-8. [PMID: 22078554 DOI: 10.1016/j.str.2011.10.010] [Citation(s) in RCA: 159] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 10/21/2011] [Accepted: 10/24/2011] [Indexed: 12/01/2022]
Abstract
Although cell membranes are packed with proteins mingling with lipids, remarkably little is known about how proteins interact with lipids to carry out their function. Novel analytical tools are revealing the astounding diversity of lipids in membranes. The issue is now to understand the cellular functions of this complexity. In this Perspective, we focus on the interface of integral transmembrane proteins and membrane lipids in eukaryotic cells. Clarifying how proteins and lipids interact with each other will be important for unraveling membrane protein structure and function. Progress toward this goal will be promoted by increasing overlap between different fields that have so far operated without much crosstalk.
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Affiliation(s)
- Unal Coskun
- Max Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstraße 108 Dresden, Germany.
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30
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Cholesterol depletion of hepatoma cells impairs hepatitis B virus envelopment by altering the topology of the large envelope protein. J Virol 2011; 85:13373-83. [PMID: 21994451 DOI: 10.1128/jvi.05423-11] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous reports have shown that cholesterol depletion of the membrane envelope of the hepatitis B virus (HBV) impairs viral infection of target cells. A potential function of this lipid in later steps of the viral life cycle remained controversial, with secretion of virions and subviral particles (SVP) being either inhibited or not affected, depending on the experimental approach employed to decrease the intracellular cholesterol level. This work addressed the role of host cell cholesterol on HBV replication, assembly, and secretion, using an alternative method to inhibition of the enzymes involved in the biosynthesis pathway. Growing HBV-producing cells with lipoprotein-depleted serum (LPDS) resulted in an important reduction of the amount of cholesterol within 24 h of treatment (about 40%). Cell exposure to chlorpromazine, an inhibitor of the clathrin-mediated pathway used by the low-density lipoprotein receptor for endocytosis, also impacted the cholesterol level; however, this level of inhibition was not achievable when the synthesis inhibitor lovastatin was used. HBV secretion was significantly inhibited in cholesterol-depleted cells (by ∼80%), while SVP release remained unaffected. The viral DNA genome accumulated in LPDS-treated cells in a time-dependent manner. Specific immunoprecipitation of nucleocapsids and mature virions revealed an increased amount of naked nucleocapsids, while synthesis of the envelope proteins occurred as normally. Following analysis of the large envelope protein conformation in purified microsomes, we concluded that cholesterol is important in maintaining the dual topology of this polypeptide, which is critical for viral envelopment.
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31
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Roongta UV, Pabalan JG, Wang X, Ryseck RP, Fargnoli J, Henley BJ, Yang WP, Zhu J, Madireddi MT, Lawrence RM, Wong TW, Rupnow BA. Cancer cell dependence on unsaturated fatty acids implicates stearoyl-CoA desaturase as a target for cancer therapy. Mol Cancer Res 2011; 9:1551-61. [PMID: 21954435 DOI: 10.1158/1541-7786.mcr-11-0126] [Citation(s) in RCA: 196] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Emerging literature suggests that metabolic pathways play an important role in the maintenance and progression of human cancers. In particular, recent studies have implicated lipid biosynthesis and desaturation as a requirement for tumor cell survival. In the studies reported here, we aimed to understand whether tumor cells require the activity of either human isoform of stearoyl-CoA-desaturase (SCD1 or SCD5) for survival. Inhibition of SCD1 by siRNA or a small molecule antagonist results in strong induction of apoptosis and growth inhibition, when tumor cells are cultured in reduced (2%) serum conditions, but has little impact on cells cultured in 10% serum. Depletion of SCD5 had minimal effects on cell growth or apoptosis. Consistent with the observed dependence on SCD1, but not SCD5, levels of SCD1 protein increased in response to decreasing serum levels. Both induction of SCD1 protein and sensitivity to growth inhibition by SCD1 inhibition could be reversed by supplementing growth media with unsaturated fatty acids, the product of the enzymatic reaction catalyzed by SCD1. Transcription profiling of cells treated with an SCD inhibitor revealed strong induction of markers of endoplasmic reticulum stress. Underscoring its importance in cancer, SCD1 protein was found to be highly expressed in a large percentage of human cancer specimens. SCD inhibition resulted in tumor growth delay in a human gastric cancer xenograft model. Altogether, these results suggest that desaturated fatty acids are required for tumor cell survival and that SCD may represent a viable target for the development of novel agents for cancer therapy.
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Affiliation(s)
- Urvashi V Roongta
- Department of Oncology Drug Discovery, Bristol-Myers Squibb R&D, Princeton, NJ 08543, USA
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Lateral sorting in model membranes by cholesterol-mediated hydrophobic matching. Proc Natl Acad Sci U S A 2011; 108:16628-33. [PMID: 21930944 DOI: 10.1073/pnas.1103742108] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Theoretical studies predict hydrophobic matching between transmembrane domains of proteins and bilayer lipids to be a physical mechanism by which membranes laterally self-organize. We now experimentally study the direct consequences of mismatching of transmembrane peptides of different length with bilayers of different thicknesses at the molecular level. In both model membranes and simulations we show that cholesterol critically constrains structural adaptations at the peptide-lipid interface under mismatch. These constraints translate into a sorting potential and lead to selective lateral segregation of peptides and lipids according to their hydrophobic length.
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Deguil J, Pineau L, Rowland Snyder EC, Dupont S, Beney L, Gil A, Frapper G, Ferreira T. Modulation of lipid-induced ER stress by fatty acid shape. Traffic 2011; 12:349-62. [PMID: 21143717 DOI: 10.1111/j.1600-0854.2010.01150.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Exposure of pancreatic β cells to long-chain saturated fatty acids (SFA) induces a so-called endoplasmic reticulum (ER) stress that can ultimately lead to cell death. This process is believed to participate in insulin deficiency associated with type 2 diabetes, via a decrease in β-cell mass. By contrast, some unsaturated fatty acid species appear less toxic to the cells and can even alleviate SFA-induced ER stress. In the present study, we took advantage of a simple yeast-based model, which brings together most of the trademarks of lipotoxicity in human cells, to screen fatty acids of various structures for their capacity to counter ER stress. Here we demonstrate that the tendency of a free fatty acid (FFA) to reduce SFA toxicity depends on a complex conjunction of parameters, including chain length, level of unsaturation, position of the double bonds and nature of the isomers (cis or trans). Interestingly, potent FFA act as building blocks for phospholipid synthesis and help to restore an optimal membrane organization, compatible with ER function and normal protein trafficking.
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Affiliation(s)
- Julie Deguil
- Institut de Physiologie et Biologie Cellulaires, Université de POITIERS, CNRS UMR 6187, 40 Avenue du Recteur Pineau, 86022 Poitiers, France
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Wang Q, Shinkre BA, Lee JG, Weniger MA, Liu Y, Chen W, Wiestner A, Trenkle WC, Ye Y. The ERAD inhibitor Eeyarestatin I is a bifunctional compound with a membrane-binding domain and a p97/VCP inhibitory group. PLoS One 2010; 5:e15479. [PMID: 21124757 PMCID: PMC2993181 DOI: 10.1371/journal.pone.0015479] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2010] [Accepted: 09/29/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Protein homeostasis in the endoplasmic reticulum (ER) has recently emerged as a therapeutic target for cancer treatment. Disruption of ER homeostasis results in ER stress, which is a major cause of cell death in cells exposed to the proteasome inhibitor Bortezomib, an anti-cancer drug approved for treatment of multiple myeloma and Mantle cell lymphoma. We recently reported that the ERAD inhibitor Eeyarestatin I (EerI) also disturbs ER homeostasis and has anti-cancer activities resembling that of Bortezomib. METHODOLOGY AND PRINCIPAL FINDINGS Here we developed in vitro binding and cell-based functional assays to demonstrate that a nitrofuran-containing (NFC) group in EerI is the functional domain responsible for the cytotoxicity. Using both SPR and pull down assays, we show that EerI directly binds the p97 ATPase, an essential component of the ERAD machinery, via the NFC domain. An aromatic domain in EerI, although not required for p97 interaction, can localize EerI to the ER membrane, which improves its target specificity. Substitution of the aromatic module with another benzene-containing domain that maintains membrane localization generates a structurally distinct compound that nonetheless has similar biologic activities as EerI. CONCLUSIONS AND SIGNIFICANCE Our findings reveal a class of bifunctional chemical agents that can preferentially inhibit membrane-bound p97 to disrupt ER homeostasis and to induce tumor cell death. These results also suggest that the AAA ATPase p97 may be a potential drug target for cancer therapeutics.
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Affiliation(s)
- Qiuyan Wang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Bidhan A. Shinkre
- Laboratory of Cell Biochemistry and Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jin-gu Lee
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Marc A. Weniger
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Yanfen Liu
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Weiping Chen
- The Genomics Core Laboratory, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Adrian Wiestner
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - William C. Trenkle
- Laboratory of Cell Biochemistry and Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Yihong Ye
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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Pineau L, Ferreira T. Lipid-induced ER stress in yeast and β cells: parallel trails to a common fate. FEMS Yeast Res 2010; 10:1035-45. [DOI: 10.1111/j.1567-1364.2010.00674.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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36
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Cross BCS, McKibbin C, Callan AC, Roboti P, Piacenti M, Rabu C, Wilson CM, Whitehead R, Flitsch SL, Pool MR, High S, Swanton E. Eeyarestatin I inhibits Sec61-mediated protein translocation at the endoplasmic reticulum. J Cell Sci 2009; 122:4393-400. [PMID: 19903691 DOI: 10.1242/jcs.054494] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Production and trafficking of proteins entering the secretory pathway of eukaryotic cells is coordinated at the endoplasmic reticulum (ER) in a process that begins with protein translocation via the membrane-embedded ER translocon. The same complex is also responsible for the co-translational integration of membrane proteins and orchestrates polypeptide modifications that are often essential for protein function. We now show that the previously identified inhibitor of ER-associated degradation (ERAD) eeyarestatin 1 (ES(I)) is a potent inhibitor of protein translocation. We have characterised this inhibition of ER translocation both in vivo and in vitro, and provide evidence that ES(I) targets a component of the Sec61 complex that forms the membrane pore of the ER translocon. Further analyses show that ES(I) acts by preventing the transfer of the nascent polypeptide from the co-translational targeting machinery to the Sec61 complex. These results identify a novel effect of ES(I), and suggest that the drug can modulate canonical protein transport from the cytosol into the mammalian ER both in vitro and in vivo.
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Affiliation(s)
- Benedict C S Cross
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, M13 9PT, UK
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37
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Pineau L, Colas J, Dupont S, Beney L, Fleurat-Lessard P, Berjeaud JM, Bergès T, Ferreira T. Lipid-Induced ER Stress: Synergistic Effects of Sterols and Saturated Fatty Acids. Traffic 2009; 10:673-90. [DOI: 10.1111/j.1600-0854.2009.00903.x] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Affiliation(s)
- Kevin R Mackenzie
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA
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39
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Albrecht I, Gatfield J, Mini T, Jeno P, Pieters J. Essential role for cholesterol in the delivery of exogenous antigens to the MHC class I-presentation pathway. Int Immunol 2006; 18:755-65. [PMID: 16608901 DOI: 10.1093/intimm/dxl013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Cross-presentation, which is crucial for the generation of immunity against virus-infected and tumor cells, requires exogenous antigens to be internalized into antigen-presenting cells (APCs) followed by translocation to the cytosol by unknown mechanisms. One important entry route for such antigens is macropinocytosis. We here describe that cholesterol is essential for cross-presentation of antigens loaded via macropinocytosis into APCs. Modification of antigens by palmitoylation to target antigens to cholesterol-enriched plasma membrane domains resulted in a dramatically increased T cell activation. These results define cholesterol as an essential factor for cross-presentation and suggest that specific modification of antigens to increase their affinity for cholesterol may be utilized to enhance immunity.
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Affiliation(s)
- Imke Albrecht
- Biozentrum, University of Basel, Klingelbergstrasse 50, CH 4056 Basel, Switzerland
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40
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Karamyshev AL, Kelleher DJ, Gilmore R, Johnson AE, von Heijne G, Nilsson I. Mapping the interaction of the STT3 subunit of the oligosaccharyl transferase complex with nascent polypeptide chains. J Biol Chem 2005; 280:40489-93. [PMID: 16216884 DOI: 10.1074/jbc.m509168200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Many secretory and membrane proteins are N-glycosylated by the oligosaccharyl transferase complex during their translocation across the endoplasmic reticulum membrane. Several experimental observations suggest that the highly conserved STT3 subunit contains the active site of the oligosaccharyl transferase. Here, we report a detailed study of the interaction between the active site of the STT3 protein and nascent polypeptide chains using an in vitro photocrosslinking technique. Our results show that the addition of a glycan moiety in a stretch of approximately 15 residues surrounding a QK(*)T cross-linking site impairs the interaction between the nascent chain and STT3.
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Affiliation(s)
- Andrey L Karamyshev
- Department of Medical Biochemistry and Genetics, Texas A&M University System Health Science Center, USA
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41
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Black VH, Sanjay A, van Leyen K, Lauring B, Kreibich G. Cholesterol and steroid synthesizing smooth endoplasmic reticulum of adrenocortical cells contains high levels of proteins associated with the translocation channel. Endocrinology 2005; 146:4234-49. [PMID: 15947003 DOI: 10.1210/en.2005-0372] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Steroid-secreting cells are characterized by abundant smooth endoplasmic reticulum whose membranes contain many enzymes involved in sterol and steroid synthesis. Yet they have relatively little morphologically identifiable rough endoplasmic reticulum, presumably required for synthesis and maintenance of the smooth membranes. In this study, we demonstrate that adrenal smooth microsomal subfractions enriched in smooth endoplasmic reticulum membranes contain high levels of translocation apparatus and oligosaccharyltransferase complex proteins, previously thought confined to rough endoplasmic reticulum. We further demonstrate that these smooth microsomal subfractions are capable of effecting cotranslational translocation, signal peptide cleavage, and N-glycosylation of newly synthesized polypeptides. This shifts the paradigm for distinction between smooth and rough endoplasmic reticulum. Confocal microscopy revealed the proteins to be distributed throughout the abundant tubular endoplasmic reticulum in these cells, which is predominantly smooth surfaced. We hypothesize that the broadly distributed translocon and oligosaccharyltransferase proteins participate in local synthesis and/or quality control of membrane proteins involved in cholesterol and steroid metabolism in a sterol-dependent and hormonally regulated manner.
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Affiliation(s)
- Virginia H Black
- Department of Cell Biology and Kaplan Cancer Center, New York University School of Medicine, 550 First Avenue, New York, New York 10016, USA.
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Abstract
A number of protein toxins of bacterial and plant origin have cytosolic targets, and knowledge about these toxins have provided us with essential information about mechanisms that can be used to gain access to the cytosol as well as detailed knowledge about endocytosis and intracellular sorting. Such toxins include those that have two moieties, one (the B-moiety) that binds to cell surface receptors and another (the A-moiety) with enzymatic activity that enters the cytosol, as well as molecules that only have the enzymatically active moiety and therefore are inefficient in cell entry. The toxins discussed in the present article include bacterial toxins such as Shiga toxin and diphtheria toxin, as well as plant toxins such as ricin and ribosome-inactivating proteins without a binding moiety, such as gelonin. Toxins with a binding moiety can be used as vectors to translocate epitopes, intact proteins, and even nucleotides into the cytosol. The toxins fall into two main groups when it comes to cytosolic entry. Some toxins enter from endosomes in response to low endosomal pH, whereas others, including Shiga toxin and ricin, are transported all the way to the Golgi apparatus and the ER before they are translocated to the cytosol. Plant proteins such as gelonin that are without a binding moiety are taken up only by fluid-phase endocytosis, and normally they have a low toxicity. However, they can be used to test for disruption of endosomal membranes leading to cytosolic access of internalized molecules. Similarly to toxins with a binding moiety they are highly toxic when reaching the cytosol, thereby providing the investigator with an efficient tool to study endosomal disruption and induced transport to the cytosol. In conclusion, the protein toxins are useful tools to study transport and cytosolic translocation, and they can be used as vectors for transport to the interior of the cell.
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Affiliation(s)
- K Sandvig
- Institute for Cancer Research, The Norwegian Radium Hospital, University of Oslo, Montebello
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Brambillasca S, Yabal M, Soffientini P, Stefanovic S, Makarow M, Hegde RS, Borgese N. Transmembrane topogenesis of a tail-anchored protein is modulated by membrane lipid composition. EMBO J 2005; 24:2533-42. [PMID: 15973434 PMCID: PMC1176458 DOI: 10.1038/sj.emboj.7600730] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Accepted: 06/06/2005] [Indexed: 11/08/2022] Open
Abstract
A large class of proteins with cytosolic functional domains is anchored to selected intracellular membranes by a single hydrophobic segment close to the C-terminus. Although such tail-anchored (TA) proteins are numerous, diverse, and functionally important, the mechanism of their transmembrane insertion and the basis of their membrane selectivity remain unclear. To address this problem, we have developed a highly specific, sensitive, and quantitative in vitro assay for the proper membrane-spanning topology of a model TA protein, cytochrome b5 (b5). Selective depletion from membranes of components involved in cotranslational protein translocation had no effect on either the efficiency or topology of b5 insertion. Indeed, the kinetics of transmembrane insertion into protein-free phospholipid vesicles was the same as for native ER microsomes. Remarkably, loading of either liposomes or microsomes with cholesterol to levels found in other membranes of the secretory pathway sharply and reversibly inhibited b5 transmembrane insertion. These results identify the minimal requirements for transmembrane topogenesis of a TA protein and suggest that selectivity among various intracellular compartments can be imparted by differences in their lipid composition.
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Affiliation(s)
- Silvia Brambillasca
- CNR Institute of Neuroscience – Cell Mol Pharmacology – and Department of Medical Pharmacology, University of Milan, Milan, Italy
| | - Monica Yabal
- Program of Cellular Biotechnology, Institute of Biotechnology and Department of Applied Chemistry and Microbiology, University of Helsinki, Helsinki, Finland
| | - Paolo Soffientini
- CNR Institute of Neuroscience – Cell Mol Pharmacology – and Department of Medical Pharmacology, University of Milan, Milan, Italy
| | - Sandra Stefanovic
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Marja Makarow
- Program of Cellular Biotechnology, Institute of Biotechnology and Department of Applied Chemistry and Microbiology, University of Helsinki, Helsinki, Finland
| | - Ramanujan S Hegde
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
- Cell Biology and Metabolism Branch, NICHD, National Institutes of Health, 18 Library Drive, Bldg. 18, Room 101, Bethesda, MD 20892, USA. Tel.: +1 301 496 4855; Fax: +1 301 402 0078; E-mail:
| | - Nica Borgese
- CNR Institute of Neuroscience – Cell Mol Pharmacology – and Department of Medical Pharmacology, University of Milan, Milan, Italy
- Faculty of Pharmacy, University of Catanzaro Magna Graecia, Roccelletta di Borgia (CZ), Italy
- CNR Institute of Neuroscience/Cell Mol Pharmacology, via Vanvitelli 32, 20129 Milano, Italy. Tel.: +39 02 503 16971; Fax: +39 02 749 0574; E-mail:
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Baumann NA, Sullivan DP, Ohvo-Rekilä H, Simonot C, Pottekat A, Klaassen Z, Beh CT, Menon AK. Transport of newly synthesized sterol to the sterol-enriched plasma membrane occurs via nonvesicular equilibration. Biochemistry 2005; 44:5816-26. [PMID: 15823040 DOI: 10.1021/bi048296z] [Citation(s) in RCA: 178] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanism by which newly synthesized sterols are transported from their site of synthesis, the endoplasmic reticulum (ER), to the sterol-enriched plasma membrane (PM) is not fully understood. Studies in mammalian cells suggest that newly synthesized cholesterol is transported to the PM in Golgi-bypassing vesicles and/or via a nonvesicular process. Using the yeast Saccharomyces cerevisiae as a model system, we now rule out an essential role for known vesicular transport pathways in transporting the major yeast sterol, ergosterol, from its site of synthesis to the PM. We use a cyclodextrin-based sterol capture assay to show that transport of newly synthesized ergosterol to the PM is unaltered in cells defective in Sec18p, a protein required for almost all intracellular vesicular trafficking events; we also show that transport is not blocked in cells that are defective in formation of transport vesicles at the ER or in vesicle fusion with the PM. Our data suggest instead that transport occurs by equilibration (t(1/2) approximately 10-15 min) of ER and PM ergosterol pools via a bidirectional, nonvesicular process that is saturated in wild-type exponentially growing yeast. To reconcile an equilibration process with the high ergosterol concentration of the PM relative to ER, we note that a large fraction of PM ergosterol is found condensed with sphingolipids in membrane rafts that coexist with free sterol. We propose that the concentration of free sterol is similar in the PM and ER and that only free (nonraft) sterol molecules have access to a nonvesicular transport pathway that connects the two organelles. This is the first description of biosynthetic sterol transport in yeast.
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Affiliation(s)
- Nikola A Baumann
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, Wisconsin 53706, USA
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45
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Li Y, Ge M, Ciani L, Kuriakose G, Westover EJ, Dura M, Covey DF, Freed JH, Maxfield FR, Lytton J, Tabas I. Enrichment of endoplasmic reticulum with cholesterol inhibits sarcoplasmic-endoplasmic reticulum calcium ATPase-2b activity in parallel with increased order of membrane lipids: implications for depletion of endoplasmic reticulum calcium stores and apoptosis in cholesterol-loaded macrophages. J Biol Chem 2004; 279:37030-9. [PMID: 15215242 DOI: 10.1074/jbc.m405195200] [Citation(s) in RCA: 222] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Macrophages in advanced atherosclerotic lesions accumulate large amounts of unesterified, or "free," cholesterol (FC). FC accumulation induces macrophage apoptosis, which likely contributes to plaque destabilization. Apoptosis is triggered by the enrichment of the endoplasmic reticulum (ER) with FC, resulting in depletion of ER calcium stores, and induction of the unfolded protein response. To explain the mechanism of ER calcium depletion, we hypothesized that FC enrichment of the normally cholesterol-poor ER membrane inhibits the macrophage ER calcium pump, sarcoplasmic-endoplasmic reticulum calcium ATPase-2b (SERCA2b). FC enrichment of ER membranes to a level similar to that occurring in vivo inhibited both the ATPase activity and calcium sequestration function of SERCA2b. Enrichment of ER with ent-cholesterol or 14:0-18:0 phosphatidylcholine, which possess the membrane-ordering properties of cholesterol, also inhibited SERCA2b. Moreover, at various levels of FC enrichment of ER membranes, there was a very close correlation between increasing membrane lipid order, as monitored by 16-doxyl-phosphatidycholine electron spin resonance, and SERCA2b inhibition. In view of these data, we speculate that SERCA2b, a conformationally active protein with 11 membrane-spanning regions, loses function due to decreased conformational freedom in FC-ordered membranes. This biophysical model may underlie the critical connection between excess cholesterol, unfolded protein response induction, macrophage death, and plaque destabilization in advanced atherosclerosis.
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Affiliation(s)
- Yankun Li
- Department of Medicine, Columbia University, 630 West 168th Street, New York, NY 10032, USA
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Montoudis A, Simoneau L, Lafond J. Influence of a maternal cholesterol-enriched diet on [1-14C]-linoleic acid and L-[4, 5-3H]-leucine entry in plasma of rabbit offspring. Life Sci 2004; 74:1751-62. [PMID: 14741733 DOI: 10.1016/j.lfs.2003.08.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Fetal development requires an important entry of essential free fatty acids (EFFA) and essential amino acids (EAA) into the fetal circulation. We have reported that a 0.2% enriched-cholesterol diet (ECD) during rabbit gestation significantly reduces fetus weight compared to control diet. It is known that dietary linoleic acid deficiency, an EFFA, during the fetal development induces an important impair to the somatic development. Moreover, intrauterine growth retardation induced a reduction of the flux of leucine, an EAA, from maternal to fetal circulation. Therefore, we hypothesized that the administration of an ECD induces modifications of placental lipid composition concomitant alterations of the transfer of linoleic acid and leucine in fetal circulation. Quantification of placental lipids revealed that in the ECD group a reduction of total-cholesterol (TC) and free-cholesterol (FC) is observed, however an increased in FFA and phospholipids is noticed when compared to the control group. In placenta from the ECD group, the FC/ TC ratio is significantly reduced compared to the control group. In the ECD group, the liver shows an increase of TC, FC and FFA compared to the control group. However, the quantity of triacylglycerol present in the liver from the ECD is significantly reduced compared to the control group. To evaluate the placental transfer of some essential nutrients, intravenous injection of [1-14C]-linoleic acid or L-[4, 5-3H]-leucine to term rabbit (control and ECD group) were done. Two hours later, rabbits were euthanized and we collected placenta, livers and blood from dams and offspring. The concentrations of both radiolabeled molecules (linoleic acid and its esterified form or leucine) were higher in the plasma of ECD offspring than those found in offspring from control diet. Despite such alteration of placental lipid composition, linoleic acid and leucine transfer by the placenta was not compromised but rather increased.
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Affiliation(s)
- Alain Montoudis
- Laboratoire de Physiologie Materno-Foetale, Université du Québec à Montréal, Montréal, Canada, H3C 3P8
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47
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Ohashi M, Mizushima N, Kabeya Y, Yoshimori T. Localization of mammalian NAD(P)H steroid dehydrogenase-like protein on lipid droplets. J Biol Chem 2003; 278:36819-29. [PMID: 12837764 DOI: 10.1074/jbc.m301408200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Mammalian enzymes in late cholesterol biosynthesis have been localized uniformly over the endoplasmic reticulum by enzymatic methods. We report here the first mammalian cholesterol biosynthetic enzyme unequivocally localized at the surface of intracellular lipid storage droplets. NAD(P)H steroid dehydrogenase-like protein (Nsdhl), a mammalian C-3 sterol dehydrogenase involved in the conversion of lanosterol into cholesterol, was localized on lipid droplets by immunofluorescence microscopy and subcellular fractionation. Nsdhl was localized on lipid droplets even when cell growth exclusively depended on cholesterol biosynthesis mediated by this enzyme. Depletion of fatty acids in culture medium reduced the development of lipid droplets and caused Nsdhl redistribution to the endoplasmic reticulum. Elevating oleic acid in medium induced well developed, Nsdhl-positive lipid droplets, and simultaneously caused a reduction in cellular conversion of lanosterol into cholesterol. Manipulated human NSDHL with a missense mutation (G205S) causing a human embryonic developmental disorder, congenital hemidysplasia with ichthyosiform nevus and limb defects (CHILD) syndrome, could no longer be localized on lipid droplets. Although the expression of wild-type NSDHL could restore the defective growth of a CHO cholesterol auxotroph, LEX2 in cholesterol-deficient medium, the expression of NSDHL(G205S) failed to do so. These results point to functional significance of the localization of Nsdhl on lipid droplets. Functional significance was also suggested by the colocalization of Nsdhl on lipid droplets with TIP47, a cargo selection protein for mannose 6-phosphate receptors from late endosomes to the trans-Golgi network. These results add to the growing notion that the lipid droplet is an organelle endowed with more complex roles in various biological phenomena.
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Affiliation(s)
- Masato Ohashi
- Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan.
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Higgins MA, Berridge BR, Mills BJ, Schultze AE, Gao H, Searfoss GH, Baker TK, Ryan TP. Gene expression analysis of the acute phase response using a canine microarray. Toxicol Sci 2003; 74:470-84. [PMID: 12773757 DOI: 10.1093/toxsci/kfg142] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The safety of pharmaceuticals is typically assessed in the dog and rat prior to investigation in humans. As a result, a greater understanding of adverse effects in these preclinical testing species would improve safety assessment. Despite this need, there is a lack of tools to examine mechanisms and identify biomarkers in the dog. To address this issue, we developed an Affymetrix-based oligonucleotide microarray capable of monitoring the expression of thousands of canine genes in parallel. The custom canine array contains 22,774 probe sets, consisting of 13,729 canine and 9045 human-derived probe sets. To improve cross-species hybridization with human-derived probes, the detection region was moved from the variable 3' UTR to the more homologous coding region. Testing of this strategy was accomplished by comparing hybridization of naive dog liver RNA to the canine array (coding region design) and human U133A array (standard 3' design). Although raw signal intensity was greater with canine-specific probe sets, human-derived probes detected the expression of additional liver transcripts. To assess the ability of this tool to detect differential gene expression, the acute phase response was examined in beagle dogs given lipopolysaccharide (LPS). Hepatic gene expression 4 and 24 h post-LPS administration was compared to gene expression profiles of vehicle-treated dogs (n=3/group). Array data was consistent with an acute inflammatory response, with transcripts for multiple cytokines and acute phase proteins markedly induced 4 h after LPS challenge. Robust changes in the expression of transcripts involved with glucose homeostasis, biotransformation, and extracellular matrix remodeling were observed 24 h post-dose. In addition, the canine array identified several potential biomarkers of hepatic inflammation. Strong correlations were found between gene expression data and alterations in clinical chemistry parameters such as serum amyloid A (SAA), albumin, and alkaline phosphatase (ALP). In summary, this new genomic tool successfully detected basal canine gene expression and identified novel aspects of the acute phase response in dog that shed new light on mechanisms underlying inflammatory processes.
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Affiliation(s)
- M A Higgins
- Department of Lead Optimization Toxicology, Lilly Research Laboratories, Eli Lilly and Company, Greenfield, IN 46140, USA
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49
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Römisch K, Collie N, Soto N, Logue J, Lindsay M, Scheper W, Cheng CHC. Protein translocation across the endoplasmic reticulum membrane in cold-adapted organisms. J Cell Sci 2003; 116:2875-83. [PMID: 12771183 DOI: 10.1242/jcs.00597] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Secretory proteins enter the secretory pathway by translocation across the membrane of the endoplasmic reticulum (ER) via a channel formed primarily by the Sec61 protein. Protein translocation is highly temperature dependent in mesophilic organisms. We asked whether the protein translocation machinery of organisms from extremely cold habitats was adapted to function at low temperature and found that post-translational protein import into ER-derived microsomes from Antarctic yeast at low temperature was indeed more efficient than into mesophilic yeast microsomes. Analysis of the amino-acid sequences of the core component of the protein translocation channel, Sec61p, from Antarctic yeast species did not reveal amino-acid changes potentially adaptive for function in the cold, because the sequences were too divergent. We therefore analyzed Sec61alpha (vertebrate Sec61p) sequences and protein translocation into the ER of Antarctic and Arctic fishes and compared them to Sec61alpha and protein translocation into the ER of temperate-water fishes and mammals. Overall, Sec61alpha is highly conserved amongst these divergent taxa; a number of amino-acid changes specific to fishes are evident throughout the protein, and, in addition, changes specific to cold-water fishes cluster in the lumenal loop between transmembrane domains 7 and 8 of Sec61alpha, which is known to be important for protein translocation across the ER membrane. Secretory proteins translocated more efficiently into fish microsomes than into mammalian microsomes at 10 degrees C and 0 degrees C. The efficiency of protein translocation at 0 degrees C was highest for microsomes from a cold-water fish. Despite substantial differences in ER membrane lipid composition, ER membrane fluidity was identical in Antarctic fishes, mesophilic fishes and warm-blooded vertebrates, suggesting that membrane fluidity, although typically important for the function of the transmembrane proteins, is not limiting for protein translocation across the ER membrane in the cold. Collectively, our data suggest that the limited amino-acid changes in Sec61alpha from fishes may be functionally significant and represent adaptive changes that enhance channel function in the cold.
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Affiliation(s)
- Karin Römisch
- University of Cambridge, CIMR, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 2XY, UK.
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Nilsson I, Kelleher DJ, Miao Y, Shao Y, Kreibich G, Gilmore R, von Heijne G, Johnson AE. Photocross-linking of nascent chains to the STT3 subunit of the oligosaccharyltransferase complex. J Cell Biol 2003; 161:715-25. [PMID: 12756234 PMCID: PMC2199356 DOI: 10.1083/jcb.200301043] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In eukaryotic cells, polypeptides are N glycosylated after passing through the membrane of the ER into the ER lumen. This modification is effected cotranslationally by the multimeric oligosaccharyltransferase (OST) enzyme. Here, we report the first cross-linking of an OST subunit to a nascent chain that is undergoing translocation through, or integration into, the ER membrane. A photoreactive probe was incorporated into a nascent chain using a modified Lys-tRNA and was positioned in a cryptic glycosylation site (-Q-K-T- instead of -N-K-T-) in the nascent chain. When translocation intermediates with nascent chains of increasing length were irradiated, nascent chain photocross-linking to translocon components, Sec61alpha and TRAM, was replaced by efficient photocross-linking solely to a protein identified by immunoprecipitation as the STT3 subunit of the OST. No cross-linking was observed in the absence of a cryptic sequence or in the presence of a competitive peptide substrate of the OST. As no significant nascent chain photocross-linking to other OST subunits was detected in these fully assembled translocation and integration intermediates, our results strongly indicate that the nascent chain portion of the OST active site is located in STT3.
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Affiliation(s)
- IngMarie Nilsson
- Department of Medical Biochemistry and Genetics, Texas A&M University System Health Science Center, College Station, TX 77843, USA
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