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Pattnaik GP, Chakraborty H. Cholesterol: A key player in membrane fusion that modulates the efficacy of fusion inhibitor peptides. VITAMINS AND HORMONES 2021; 117:133-155. [PMID: 34420578 DOI: 10.1016/bs.vh.2021.06.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The interaction of cholesterol with the neighboring lipids modulates several physical properties of the membrane. Mostly, it affects membrane fluidity, membrane permeability, lateral diffusion of lipids, bilayer thickness, and water penetration into the lipid bilayer. Due to the smaller head group to hydrophobic cross-sectional area of the tail, cholesterol induces intrinsic negative curvature to the membrane. The interaction of cholesterol with sphingolipids forms lipid rafts; generates phase separation in the membrane. The cholesterol-dependent modifications of membrane physical properties modulate viral infections by affecting the fusion between viral and host cell membranes. Cholesterol demonstrates a strong impact on the structure, depth of penetration, conformation, and organization of fusion peptides in membrane milieu. Further, cholesterol has been implicated to modify the fusion inhibitory efficiency of peptide-based membrane fusion inhibitors.
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Affiliation(s)
| | - Hirak Chakraborty
- School of Chemistry, Sambalpur University, Burla, Odisha, India; Centre of Excellence in Natural Products and Therapeutics, Sambalpur University, Burla, Odisha, India.
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2
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Adar T, Shankar Lankalapalli R, Bittman R, Ilan Y. The assembly of glycosphingolipid determines their immunomodulatory effect: A novel method for structure-based design of immunotherapy. Cell Immunol 2020; 355:104157. [PMID: 32659503 DOI: 10.1016/j.cellimm.2020.104157] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 05/27/2020] [Accepted: 07/01/2020] [Indexed: 11/18/2022]
Abstract
Structure-activity relationships provide insight into the binding interactions of beta-glycosphingolipids (GSLs) with both the TCR and the CD1d molecules, as well as the subsequent immunologic response of regulatory NKT cells. AIM To determine the effects of synthetic GSL structures on their immune modulatory functions. METHODS GSLs of various structures were tested in vitro and in an animal model of Concanavalin A (ConA) immune-mediated hepatitis. RESULTS In vitro, using SV40 binding to live monkey CV1 cells, the l-threo stereoisomer of C8-β-LacCer inhibits caveolar internalization, reducing viral binding to the cell surface. In vivo, in the ConA model, LR172, which has a saturated C8 chain, and LR178, which has a trans double bond at C-2 in the C8 chain, suppressed the immune-mediated liver inflammation and reduced IFNγ levels in a dose dependent manner. The beneficial effects of LR172 and of LR178 are associated with suppression of liver apoptosis, increased phosphorylated STAT3 expression in the liver, and an increase in the NKT liver/spleen ratio. SUMMARY The assembly of GSLs determines their immunomodulatory effect and can serve as a method for structure-based design of immunotherapy.
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Affiliation(s)
- Tomer Adar
- Department of Medicine, Hadassah Hebrew University Medical Center, Jerusalem, Israel
| | - Ravi Shankar Lankalapalli
- Department of Chemistry & Biochemistry, Queens College of the City University of New York, United States; Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram 695019, Kerala, India
| | - Robert Bittman
- Department of Chemistry & Biochemistry, Queens College of the City University of New York, United States
| | - Yaron Ilan
- Department of Medicine, Hadassah Hebrew University Medical Center, Jerusalem, Israel.
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3
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Sousa IP, Carvalho CAM, Mendes YS, Weissmuller G, Oliveira AC, Gomes AMO. Fusion of a New World Alphavirus with Membrane Microdomains Involving Partially Reversible Conformational Changes in the Viral Spike Proteins. Biochemistry 2017; 56:5823-5830. [PMID: 28956592 DOI: 10.1021/acs.biochem.7b00650] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alphaviruses are enveloped arboviruses mainly proposed to infect host cells by receptor-mediated endocytosis followed by fusion between the viral envelope and the endosomal membrane. The fusion reaction is triggered by low pH and requires the presence of both cholesterol and sphingolipids in the target membrane, suggesting the involvement of lipid rafts in the cell entry mechanism. In this study, we show for the first time the interaction of an enveloped virus with membrane microdomains isolated from living cells. Using Mayaro virus (MAYV), a New World alphavirus, we verified that virus fusion to these domains occurred to a significant extent upon acidification, although its kinetics was quite slow when compared to that of fusion with artificial liposomes demonstrated in a previous work. Surprisingly, when virus was previously exposed to acidic pH, a condition previously shown to inhibit alphavirus binding and fusion to target membranes as well as infectivity, and then reneutralized, its ability to fuse with membrane microdomains at low pH was retained. Interestingly, this observation correlated with a partial reversion of low pH-induced conformational changes in viral proteins and retention of virus infectivity upon reneutralization. Our results suggest that MAYV entry into host cells could alternatively involve internalization via lipid rafts and that the conformational changes triggered by low pH in the viral spike proteins during the entry process are partially reversible.
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Affiliation(s)
- Ivanildo P Sousa
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde and ‡Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro , Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Carlos A M Carvalho
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde and ‡Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro , Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Ygara S Mendes
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde and ‡Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro , Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Gilberto Weissmuller
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde and ‡Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro , Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Andréa C Oliveira
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde and ‡Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro , Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Andre M O Gomes
- Instituto de Bioquímica Médica Leopoldo de Meis, Centro de Ciências da Saúde and ‡Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro , Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
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4
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A reflection of the lasting contributions from Dr. Robert Bittman to sterol trafficking, sphingolipid and phospholipid research. Prog Lipid Res 2015; 61:19-29. [PMID: 26584871 DOI: 10.1016/j.plipres.2015.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 10/21/2015] [Accepted: 10/28/2015] [Indexed: 10/22/2022]
Abstract
With the passing of Dr. Robert Bittman from pancreatic cancer on the 1st October 2014, the lipid research field lost one of the most influential and significant personalities. Robert Bittman's genius was in chemical design and his contribution to the lipid research field was truly immense. The reagents and chemicals he designed and synthesised allowed interrogation of the role of lipids in constituting complex biophysical membranes, sterol transfer and in cellular communication networks. Here we provide a review of these works which serve as a lasting memory to his life.
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5
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van Duijl-Richter MKS, Blijleven JS, van Oijen AM, Smit JM. Chikungunya virus fusion properties elucidated by single-particle and bulk approaches. J Gen Virol 2015; 96:2122-2132. [DOI: 10.1099/vir.0.000144] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Mareike K. S. van Duijl-Richter
- Department of Medical Microbiology, University Medical Center Groningen, University of Groningen, 9700 RB Groningen, The Netherlands
| | - Jelle S. Blijleven
- Centre for Synthetic Biology, Zernike Institute of Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Antoine M. van Oijen
- Centre for Synthetic Biology, Zernike Institute of Advanced Materials, University of Groningen, 9747 AG Groningen, The Netherlands
- School of Chemistry, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Jolanda M. Smit
- Department of Medical Microbiology, University Medical Center Groningen, University of Groningen, 9700 RB Groningen, The Netherlands
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6
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Haid S, Pietschmann T, Pécheur EI. Low pH-dependent hepatitis C virus membrane fusion depends on E2 integrity, target lipid composition, and density of virus particles. J Biol Chem 2009; 284:17657-67. [PMID: 19411248 DOI: 10.1074/jbc.m109.014647] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Hepatitis C virus (HCV) is an enveloped, positive strand RNA virus of about 9.6 kb. Like all enveloped viruses, the HCV membrane fuses with the host cell membrane during the entry process and thereby releases the genome into the cytoplasm, initiating the viral replication cycle. To investigate the features of HCV membrane fusion, we developed an in vitro fusion assay using cell culture-produced HCV and fluorescently labeled liposomes. With this model we could show that HCV-mediated fusion can be triggered in a receptor-independent but pH-dependent manner and that fusion of the HCV particles with liposomes is dependent on the viral dose and on the lipid composition of the target membranes. In addition CBH-5, an HCV E2-specific antibody, inhibited fusion in a dose-dependent manner. Interestingly, point mutations in E2, known to abrogate HCV glycoprotein-mediated fusion in a cell-based assay, altered or even abolished fusion in the liposome-based assay. When assaying the fusion properties of HCV particles with different buoyant density, we noted higher fusogenicity of particles with lower density. This could be attributable to inherently different properties of low density particles, to association of these particles with factors stimulating fusion, or to co-flotation of factors enhancing fusion activity in trans. Taken together, these data show the important role of lipids of both the viral and target membranes in HCV-mediated fusion, point to a crucial role played by the E2 glycoprotein in the process of HCV fusion, and reveal an important behavior of HCV of different densities with regard to fusion.
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Affiliation(s)
- Sibylle Haid
- Department for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a Joint Venture of Hannover Medical School and the Helmholtz-Centre for Infection Research, Hannover 30625, Germany
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White JM, Delos SE, Brecher M, Schornberg K. Structures and mechanisms of viral membrane fusion proteins: multiple variations on a common theme. Crit Rev Biochem Mol Biol 2008; 43:189-219. [PMID: 18568847 DOI: 10.1080/10409230802058320] [Citation(s) in RCA: 664] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Recent work has identified three distinct classes of viral membrane fusion proteins based on structural criteria. In addition, there are at least four distinct mechanisms by which viral fusion proteins can be triggered to undergo fusion-inducing conformational changes. Viral fusion proteins also contain different types of fusion peptides and vary in their reliance on accessory proteins. These differing features combine to yield a rich diversity of fusion proteins. Yet despite this staggering diversity, all characterized viral fusion proteins convert from a fusion-competent state (dimers or trimers, depending on the class) to a membrane-embedded homotrimeric prehairpin, and then to a trimer-of-hairpins that brings the fusion peptide, attached to the target membrane, and the transmembrane domain, attached to the viral membrane, into close proximity thereby facilitating the union of viral and target membranes. During these conformational conversions, the fusion proteins induce membranes to progress through stages of close apposition, hemifusion, and then the formation of small, and finally large, fusion pores. Clearly, highly divergent proteins have converged on the same overall strategy to mediate fusion, an essential step in the life cycle of every enveloped virus.
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Affiliation(s)
- Judith M White
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908-0732, USA.
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Teissier É, Pécheur EI. Lipids as modulators of membrane fusion mediated by viral fusion proteins. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2007; 36:887-99. [PMID: 17882414 PMCID: PMC7080115 DOI: 10.1007/s00249-007-0201-z] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Revised: 05/17/2007] [Accepted: 06/11/2007] [Indexed: 11/24/2022]
Abstract
Enveloped viruses infect host cells by fusion of viral and target membranes. This fusion event is triggered by specific glycoproteins in the viral envelope. Fusion glycoproteins belong to either class I, class II or the newly described third class, depending upon their arrangement at the surface of the virion, their tri-dimensional structure and the location within the protein of a short stretch of hydrophobic amino acids called the fusion peptide, which is able to induce the initial lipid destabilization at the onset of fusion. Viral fusion occurs either with the plasma membrane for pH-independent viruses, or with the endosomal membranes for pH-dependent viruses. Although, viral fusion proteins are parted in three classes and the subcellular localization of fusion might vary, these proteins have to act, in common, on lipid assemblies. Lipids contribute to fusion through their physical, mechanical and/or chemical properties. Lipids can thus play a role as chemically defined entities, or through their preferential partitioning into membrane microdomains called “rafts”, or by modulating the curvature of the membranes involved in the fusion process. The purpose of this review is to make a state of the art on recent findings on the contribution of cholesterol, sphingolipids and glycolipids in cell entry and membrane fusion of a number of viral families, whose members bear either class I or class II fusion proteins, or fusion proteins of the recently discovered third class.
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Affiliation(s)
- Élodie Teissier
- Structural NMR and Bioinformatics, UMR CNRS 5086, Institut de Biologie et Chimie des Protéines, IFR 128 BioSciences Lyon-Gerland, 7 passage du Vercors, 69367 Lyon, France
| | - Eve-Isabelle Pécheur
- Structural NMR and Bioinformatics, UMR CNRS 5086, Institut de Biologie et Chimie des Protéines, IFR 128 BioSciences Lyon-Gerland, 7 passage du Vercors, 69367 Lyon, France
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9
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Waarts BL, Smit JM, Aneke OJC, McInerney GM, Liljeström P, Bittman R, Wilschut J. Reversible acid-induced inactivation of the membrane fusion protein of Semliki Forest virus. J Virol 2005; 79:7942-8. [PMID: 15919953 PMCID: PMC1143635 DOI: 10.1128/jvi.79.12.7942-7948.2005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously, it has been shown that the exposure of Semliki Forest virus (SFV) to a mildly acidic environment induces a rapid and complete loss of the ability of the virus to bind and fuse to target membranes added subsequently. In the present study, incubation of SFV at low pH followed by a specific reneutralization step resulted in a partial reversion of this loss of viral fusion capacity, as assessed in a liposomal model system. Also, the ability of the viral E1 fusion protein to undergo liposome-stimulated trimerization was restored. Furthermore, acid-treated and neutralized SFV largely retained infectivity. Exposure of SFV to low pH induced dissociation of the E1/E2 heterodimer, which was not reversed upon neutralization. It is concluded that the SFV E1 fusion protein, after acid-induced dissociation from E2, rapidly adopts an intermediate, nontrimeric conformation in which it is no longer able to interact with target membrane lipids. Neutralization restores the ability of E1 to interact with membranes. This interaction, however, remains strictly dependent on low pH.
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Affiliation(s)
- Barry-Lee Waarts
- Department of Medical Microbiology, Molecular Virology Section, University Medical Center Groningen, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands
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10
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Brockman HL, Momsen MM, Brown RE, He L, Chun J, Byun HS, Bittman R. The 4,5-double bond of ceramide regulates its dipole potential, elastic properties, and packing behavior. Biophys J 2005; 87:1722-31. [PMID: 15345551 PMCID: PMC1304577 DOI: 10.1529/biophysj.104.044529] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The biological activities of ceramides show a large variation with small changes in molecular structure. To help understand how the structure regulates the activity of this important lipid second messenger, we investigated the interfacial features of a series of synthetic ceramide analogs in monomolecular films at the argon-buffer interface. To minimize differences arising from the N-acyl moiety, each analog had either a N-hexadecanoyl or a N-cis-4-hexadecenoyl moiety amide linked to the nitrogen of the sphingosine backbone. We found that the trans 4,5-unsaturation in the sphingosine backbone promoted closer packing and lower compressibilities of ceramide analogs in interfaces relative to comparable saturated species. Moreover, structures with this feature exhibited dipole potentials as much as 150-250 mV higher than comparable compounds lacking 4,5-unsaturation. The results support the hypothesis by M.C. Yappert and co-workers that trans unsaturation in the vicinity of C4 of the sphingoid backbone augments intramolecular hydration/hydrogen bonding in the polar region. This intramolecular hydration may allow the close packing of the ceramide molecules and engender their high dipole potentials. These properties of ceramides and their analogs may be important determinants of biological function.
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Affiliation(s)
- Howard L Brockman
- The Hormel Institute, University of Minnesota, Austin, Minnesota 55912, USA.
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11
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Bittman R. The 2003 ASBMB-Avanti Award in Lipids Address: Applications of novel synthetic lipids to biological problems. Chem Phys Lipids 2004; 129:111-31. [PMID: 15081855 DOI: 10.1016/j.chemphyslip.2004.01.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2004] [Revised: 01/24/2004] [Accepted: 01/28/2004] [Indexed: 01/10/2023]
Abstract
This paper is an overview of the 2003 Avanti Award in Lipids address that was presented by Robert Bittman at the American Society for Biochemistry and Molecular Biology (ASBMB) Annual Meeting held in San Diego, CA in conjunction with meetings of five other FASEB Societies, April 15, 2003. The theme of the lecture is: "How can the chemical synthesis of unnatural lipids provide insights into problems ranging from cell biology to biophysics?" The following examples are presented: (1) novel ceramide analogs as experimental anticancer agents, (2) photoactivatable sphingosine 1-phosphate analogs as probes of protein targets of this bioactive lipid, (3) a 13C-enriched cerebroside as a quantitative probe of glycosphingolipid (GSL) transbilayer distribution in bilayers with and without sphingomyelin, (4) cis and trans unsaturated sphingomyelin analogs as modulators of the existence of cholesterol-enriched microdomains (rafts) that may facilitate fusion of alphaviruses with target membranes, (5) ceramide as an indirect enhancer of the permeabilization of membranes induced by cholesterol-specific cytolysins, (6) fluorescent GSL analogs of widely disparate structure as probes of the molecular features responsible for the selective internalization of GSLs in caveolae of living mammalian cells, (7) enantiomeric lysophosphatidic acid (LPA) analogs as probes of receptor subtypes that mediate LPA signaling, and (8) phosphonocholine analogs of the antitumor ether lipid ET-18-OCH3 as tools for discerning the primary targets that are critical for cytotoxic activity in tumor cells.
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Affiliation(s)
- Robert Bittman
- Department of Chemistry and Biochemistry, Queens College and The Graduate School of The City University of New York, Flushing, NY 11367, USA.
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12
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Smit JM, Waarts BL, Bittman R, Wilschut J. Liposomes as target membranes in the study of virus receptor interaction and membrane fusion. Methods Enzymol 2003; 372:374-92. [PMID: 14610825 DOI: 10.1016/s0076-6879(03)72022-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Affiliation(s)
- Jolanda M Smit
- Department of Medical Microbiology, Molecular Virology Section, University of Groningen, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands
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13
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Samsonov AV, Chatterjee PK, Razinkov VI, Eng CH, Kielian M, Cohen FS. Effects of membrane potential and sphingolipid structures on fusion of Semliki Forest virus. J Virol 2002; 76:12691-702. [PMID: 12438595 PMCID: PMC136663 DOI: 10.1128/jvi.76.24.12691-12702.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cells expressing the E1 and E2 envelope proteins of Semliki Forest virus (SFV) were fused to voltage-clamped planar lipid bilayer membranes at low pH. Formation and evolution of fusion pores were electrically monitored by capacitance measurements, and membrane continuity was tracked by video fluorescence microscopy by including rhodamine-phosphatidylethanolamine in the bilayer. Fusion occurred without leakage for a negative potential applied to the trans side of the planar membrane. When a positive potential was applied, leakage was severe, obscuring the observation of any fusion. E1-mediated cell-cell fusion occurred without leakage for negative intracellular potentials but with substantial leakage for zero membrane potential. Thus, negative membrane potentials are generally required for nonleaky fusion. With planar bilayers as the target, the first fusion pore that formed almost always enlarged; pore flickering was a rare event. Similar to other target membranes, fusion required cholesterol and sphingolipids in the planar membrane. Sphingosine did not support fusion, but both ceramide, with even a minimal acyl chain (C(2)-ceramide), and lysosphingomyelin (lyso-SM) promoted fusion with the same kinetics. Thus, unrelated modifications to different parts of sphingosine yielded sphingolipids that supported fusion to the same degree. Fusion studies of pyrene-labeled SFV with cholesterol-containing liposomes showed that C(2)-ceramide supported fusion while lyso-SM did not, apparently due to its positive curvature effects. A model is proposed in which the hydroxyls of C-1 and C-3 as well as N of C-2 of the sphingosine backbone must orient so as to form multiple hydrogen bonds to amino acids of SFV E1 for fusion to proceed.
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Affiliation(s)
- Andrey V Samsonov
- Department of Molecular Biophysics and Physiology, Rush Medical College, 1653 W. Congress Parkway, Chicago, IL 60612, USA
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Waarts BL, Bittman R, Wilschut J. Sphingolipid and cholesterol dependence of alphavirus membrane fusion. Lack of correlation with lipid raft formation in target liposomes. J Biol Chem 2002; 277:38141-7. [PMID: 12138173 DOI: 10.1074/jbc.m206998200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Semliki Forest virus (SFV) and Sindbis virus (SIN) are enveloped viruses that infect their host cells by receptor-mediated endocytosis and subsequent fusion from within acidic endosomes. Fusion of the viral envelope requires the presence of both cholesterol and sphingolipids in the target membrane. This is suggestive of a possible involvement of sphingolipid-cholesterol microdomains, or "lipid rafts," in the membrane fusion and cell entry process of the virus. In this study, large unilamellar vesicles (LUVs) were prepared from synthetic sphingolipids and sterols that vary with respect to their capacity to promote microdomain formation, as assessed by gradient flotation analysis in the presence of Triton X-100. SFV and SIN fused with LUVs irrespective of the presence or absence of Triton X-100-insoluble microdomains. These results suggest that SFV and SIN do not require the presence of lipid rafts for fusion with target membranes. Furthermore, it is not necessary for sphingolipids to reside in a detergent-insoluble complex with cholesterol to promote SFV or SIN fusion.
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Affiliation(s)
- Barry-Lee Waarts
- University of Groningen and Academic Hospital, Department of Medical Microbiology, Molecular Virology Section, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands
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15
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Smit JM, Li G, Schoen P, Corver J, Bittman R, Lin KC, Wilschut J. Fusion of alphaviruses with liposomes is a non-leaky process. FEBS Lett 2002; 521:62-6. [PMID: 12067727 DOI: 10.1016/s0014-5793(02)02823-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
It has been reported that low-pH-induced fusion of influenza virus with liposomes results in rapid and extensive release of both low- and high-molecular-weight substances from the liposomes [Günther-Ausborn et al., J. Biol. Chem. 270 (1995) 29279-29285; Shangguan et al., Biochemistry 35 (1996) 4956-4965]. Here, we demonstrate retention of encapsulated water-soluble compounds during fusion of Semliki Forest virus (SFV) or Sindbis virus with liposomes at low pH. Under conditions allowing complete fusion of the liposomes, a limited fluorescence dequenching of liposome-encapsulated calcein was observed, particularly for SFV. Also, radioactively labeled inulin or sucrose were largely retained. Freezing and thawing of the viruses in the absence of sucrose resulted in an enhanced leakiness of fusion. These results support the notion that the alphavirus fusion event per se is non-leaky and may well involve a discrete hemifusion intermediate.
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Affiliation(s)
- Jolanda M Smit
- Department of Medical Microbiology, Molecular Virology Section, University of Groningen and Academic Hospital, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands
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Abstract
Pyrene is one of the most frequently used lipid-linked fluorophores. Its most characteristic features are a long excited state lifetime and (local) concentration-dependent formation of excimers. Pyrene is also hydrophobic and thus does not significantly distort the conformation of the labeled lipid molecule. These characteristics make pyrene lipids well-suited for studies on a variety of biophysical phenomena like lateral diffusion, inter- or transbilayer movement of lipids and lateral organization of membranes. Pyrene lipids have also been widely employed to determine protein binding to membranes, lipid conformation and the activity of lipolytic enzymes. In cell biology, pyrene lipids are promising tools for studies on lipid trafficking and metabolism, as well as for microscopic mapping of membrane properties. The main disadvantage of pyrene lipids is the relatively large size of the fluorophore. Another disadvantage is that they require UV-excitation, which is not feasible with all microscopes.
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Affiliation(s)
- Pentti Somerharju
- Institute of Biomedicine, Biomedicum, Room C205b, Haartmaninkatu 8, P.O. Box 63, University of Helsinki, 00014 Helsinki, Finland.
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Lee P, Knight R, Smit JM, Wilschut J, Griffin DE. A single mutation in the E2 glycoprotein important for neurovirulence influences binding of sindbis virus to neuroblastoma cells. J Virol 2002; 76:6302-10. [PMID: 12021363 PMCID: PMC136218 DOI: 10.1128/jvi.76.12.6302-631-.2002] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The amino acid at position 55 of the E2 glycoprotein (E2(55)) of Sindbis virus (SV) is a critical determinant of SV neurovirulence in mice. Recombinant virus strain TE (E2(55) = histidine) differs only at this position from virus strain 633 (E2(55)= glutamine), yet TE is considerably more neurovirulent than 633. TE replicates better than 633 in a neuroblastoma cell line (N18), but similarly in BHK cells. Immunofluorescence staining showed that most N18 cells were infected by TE at a multiplicity of infection (MOI) of 50 to 500 and by 633 only at an MOI of 5,000, while both viruses infected essentially 100% of BHK cells at an MOI of 5. When exposed to pH 5, TE and 633 viruses fused to similar extents with liposomes derived from BHK or N18 cell lipids, but fusion with N18-derived liposomes was less extensive (15 to 20%) than fusion with BHK-derived liposomes ( approximately 50%). Binding of TE and 633 to N18, but not BHK, cells was dependent on the medium used for virus binding. Differences between TE and 633 binding to N18 cells were evident in Dulbecco's modified Eagle medium (DMEM), but not in RPMI. In DMEM, the binding efficiency of 633 decreased significantly as the pH was raised from 6.5 to 8.0, while that of TE did not change. The same pattern was observed with RPMI when the ionic strength of RPMI was increased to that of DMEM. TE bound better to heparin-Sepharose than 633, but this difference was not pH dependent. Growth of N18 and BHK cells in sodium chlorate to eliminate all sulfation decreased virus-cell binding, suggesting the involvement of sulfated molecules on the cell surface. Taken together, the presence of glutamine at E2(55) impairs SV binding to neural cells under conditions characteristic of interstitial fluid. We conclude that mutation to histidine participates in or stabilizes the interaction between the virus and the surface of neural cells, contributing to greater neurovirulence.
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Affiliation(s)
- Peiyu Lee
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
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18
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Tellinghuisen TL, Perera R, Kuhn RJ. Genetic and biochemical studies on the assembly of an enveloped virus. GENETIC ENGINEERING 2002; 23:83-112. [PMID: 11570108 DOI: 10.1007/0-306-47572-3_6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Affiliation(s)
- T L Tellinghuisen
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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19
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Duclos RI. The total syntheses of D-erythro-sphingosine, N-palmitoylsphingosine (ceramide), and glucosylceramide (cerebroside) via an azidosphingosine analog. Chem Phys Lipids 2001; 111:111-38. [PMID: 11457441 DOI: 10.1016/s0009-3084(01)00152-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The total synthesis of D-erythro-sphingosine (9) was performed by a chirospecific method starting from D-galactose via an azidosphingosine intermediate to give highly homogeneous (>99.9% C18:1) sphingosine base (9) which contained no observable olefin isomerization by product and was demonstrated to be optically pure by a novel method utilizing Mosher's acid. Ceramide (10) was prepared from this sphingosine (9) with highly homogeneous (99.8% C16:0) palmitic acid by two methods. The cerebroside glucosylceramide (23) was the next sphingolipid in this series to be synthesized in a highly homogeneous form. These three sphingolipids are currently being used for biophysical studies of the structures of their hydrated bio-molecular assemblies.
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Affiliation(s)
- R I Duclos
- Department of Physiology and Biophysics, Boston University School of Medicine, 715 Albany Street, 02118-2526, Boston, MA, USA.
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20
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Smit JM, Bittman R, Wilschut J. Deacylation of the transmembrane domains of Sindbis virus envelope glycoproteins E1 and E2 does not affect low-pH-induced viral membrane fusion activity. FEBS Lett 2001; 498:57-61. [PMID: 11389898 DOI: 10.1016/s0014-5793(01)02495-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The envelope glycoproteins E1 and E2 of Sindbis virus are palmitoylated at cysteine residues within their transmembrane domains (E1 at position 430, and E2 at positions 388 and 390). Here, we investigated the in vitro membrane fusion activity of Sindbis virus variants (derived from the Toto 1101 infectious clone), in which the E1 C430 and/or E2 C388/390 residues had been substituted for alanines. Both the E1 and E2 mutant viruses, as well as a triple mutant virus, fused with liposomes in a strictly low-pH-dependent manner, the fusion characteristics being indistinguishable from those of the parent Toto 1101 virus. These results demonstrate that acylation of the transmembrane domain of Sindbis virus E1 and E2 is not required for expression of viral membrane fusion activity.
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Affiliation(s)
- J M Smit
- Department of Medical Microbiology, University of Groningen, The Netherlands
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21
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Zitzer A, Bittman R, Verbicky CA, Erukulla RK, Bhakdi S, Weis S, Valeva A, Palmer M. Coupling of cholesterol and cone-shaped lipids in bilayers augments membrane permeabilization by the cholesterol-specific toxins streptolysin O and Vibrio cholerae cytolysin. J Biol Chem 2001; 276:14628-33. [PMID: 11279036 DOI: 10.1074/jbc.m100241200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vibrio cholerae cytolysin (VCC) forms oligomeric pores in lipid bilayers containing cholesterol. Membrane permeabilization is inefficient if the sterol is embedded within bilayers prepared from phosphatidylcholine only but is greatly enhanced if the target membrane also contains ceramide. Although the enhancement of VCC action is stereospecific with respect to cholesterol, we show here that no such specificity applies to the two stereocenters in ceramide; all four stereoisomers of ceramide enhanced VCC activity in cholesterol-containing bilayers. A wide variety of ceramide analogs were as effective as D-erythro-ceramide, as was diacylglycerol, suggesting that the effect of ceramide exemplifies a general trend of lipids with a small headgroup to augment the activity of VCC. Incorporation of these cone-shaped lipids into cholesterol-containing bilayers also gave similar effects with streptolysin O, another cholesterol-specific but structurally unrelated cytolysin. In contrast, the activity of staphylococcal alpha-hemolysin, which does not share with the other toxins the requirement for cholesterol, was far less affected by the presence of lipids with a conical shape. The collective data indicate that sphingolipids and glycerolipids do not interact with the cytolysins specifically. Instead, lipids that have a conical molecular shape appear to effect a change in the energetic state of membrane cholesterol that in turn augments the interaction of the sterol with the cholesterol-specific cytolysins.
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Affiliation(s)
- A Zitzer
- Institute of Medical Microbiology and Hygiene, University of Mainz, Obere Zahlbacher Strasse 67, D55101 Mainz, Germany
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22
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Hernandez R, Luo T, Brown DT. Exposure to low pH is not required for penetration of mosquito cells by Sindbis virus. J Virol 2001; 75:2010-3. [PMID: 11160702 PMCID: PMC115149 DOI: 10.1128/jvi.75.4.2010-2013.2001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
It is widely held that the penetration of cells by alphaviruses is dependent on exposure to the acid environment of an endosome. The alphavirus Sindbis virus replicates in both vertebrate and invertebrate cell cultures. We have found that exposure to an acid environment may not be required for infection of cells of the insect host. In this work, we investigated the effects of two agents (NH(4)Cl and chloroquine), which raise the pH of intracellular compartments (lysosomotropic weak bases) on the infection and replication of Sindbis virus in cells of the insect host Aedes albopictus. The results show that both of these agents increase the pH of endosomes, as indicated by protection against diphtheria toxin intoxication. NH(4)Cl blocked the production of infectious virus and blocked virus RNA synthesis when added prior to infection. Chloroquine, in contrast to its effect on vertebrate cells, had no inhibitory effect on infectious virus production in mosquito cells even when added prior to infection. Treatment with NH(4)Cl did not prevent the penetration of virus RNA into the cell cytoplasm or translation of the RNA to produce a precursor to virus nonstructural proteins. These data suggest that while these two drugs raise the pH of endosomes, they do not block insect cell penetration. These data support previous results published by our laboratory suggesting that exposure to an acid environment within the cell may not be an obligatory step in the process of infection of cells by alphaviruses.
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Affiliation(s)
- R Hernandez
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, USA
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23
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Li G, Bittman R. Synthesis of novel phenoxy-linked diazirine glycero- and sphingolipid probes via trialkylaryltin intermediates. Tetrahedron Lett 2000. [DOI: 10.1016/s0040-4039(00)01166-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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24
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Jan JT, Chatterjee S, Griffin DE. Sindbis virus entry into cells triggers apoptosis by activating sphingomyelinase, leading to the release of ceramide. J Virol 2000; 74:6425-32. [PMID: 10864654 PMCID: PMC112150 DOI: 10.1128/jvi.74.14.6425-6432.2000] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sindbis virus (SV) causes acute encephalomyelitis by infecting and inducing the death of neurons. Induction of apoptosis occurs during virus entry and involves acid-induced conformational changes in the viral surface glycoproteins and sphingomyelin (SM)-dependent fusion of the virus envelope with the endosomal membrane. We have studied neuroblastoma cells to determine how this entry process triggers cell death. Acidic sphingomyelinase was activated during entry followed by activation of neutral sphingomyelinase, SM degradation, and a sustained increase in ceramide. Ceramide-induced apoptosis and SV-induced apoptosis could be inhibited by treatment with Z-VAD-fmk, a caspase inhibitor, and by overexpression of Bcl-2, an antiapoptotic cellular protein. Acid ceramidase, expressed in a recombinant SV, decreased intracellular ceramide and protected cells from apoptosis. The data suggest that acid-induced SM-dependent virus fusion initiates the apoptotic cascade by inducing SM degradation and ceramide release.
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Affiliation(s)
- J T Jan
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205, USA
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25
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Ramstedt B, Slotte JP. Separation and purification of sphingomyelin diastereomers by high-performance liquid chromatography. Anal Biochem 2000; 282:245-9. [PMID: 10873280 DOI: 10.1006/abio.2000.4612] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
All naturally occurring sphingomyelins have the d-erythro-(2S,3R) configuration of the sphingoid base. We have developed a normal-phase HPLC method for the separation of this natural stereoisomer from the l-threo-sphingomyelin, which is the other stereoisomer commonly present in semisynthetic preparations of acyl-chain defined sphingomyelins. The chromatographic method was developed by modification of a previously reported method for phospholipid separation on a normal-phase diol column. The separation was accomplished by a binary gradient of solvent mixtures (A) hexane:isopropanol:acetic acid (82:17:1.0 by vol) and (B) isopropanol:water:acetic acid (85:14:1.0 by vol) with 0.08 vol% triethylamine added to both solvent mixtures. The program of gradient elution was optimized for maximal separation of sphingomyelin diastereomers. For detection of the lipids, a light-scattering detector was used. This analytical scale HPLC method was also used for purification of the stereoisomers (up to 0.5 mg of N-oleoyl-sphingomyelin in a single injection). The purified stereoisomers were at least 99% pure according to high-performance thin-layer chromatography and analytical HPLC.
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Affiliation(s)
- B Ramstedt
- Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, FIN 20521, Finland
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26
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Corver J, Ortiz A, Allison SL, Schalich J, Heinz FX, Wilschut J. Membrane fusion activity of tick-borne encephalitis virus and recombinant subviral particles in a liposomal model system. Virology 2000; 269:37-46. [PMID: 10725196 DOI: 10.1006/viro.1999.0172] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We present a kinetic analysis of the membrane fusion activity of tick-borne encephalitis (TBE) virus and TBE-derived recombinant subviral particles (RSPs) in a liposomal model system. Fusion was monitored using a fluorescence assay involving pyrene-labeled phospholipids. Fusion was strictly dependent on low pH, with the optimum being at pH 5.3-5.5 and the threshold at pH 6.8. Fusion did not require a protein or carbohydrate receptor in the target liposomes. Preexposure to low pH of the virus alone resulted in inactivation of its fusion activity. At the optimum pH for fusion and 37 degrees C, the rate and extent of fusion were very high, with more than 50% of the virus fusing within 2 s and the final extent of fusion being 70%. Lowering of the temperature did not result in a significant decrease in the rate and extent of fusion, suggesting that TBE virus fusion is a facile process with a low activation energy, possibly due to the flat orientation of the E glycoprotein on the viral surface facilitating the establishment of direct intermembrane contact. The fusion characteristics of TBE virus and RSPs were similar, indicating that RSPs provide a reliable and convenient model for further study of the membrane fusion properties of TBE virus.
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Affiliation(s)
- J Corver
- Laboratory of Molecular Virology, University of Groningen and Academic Hospital, Groningen, Ant. Deusinglaan 1, 9713 AV, The Netherlands
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27
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Chatterjee PK, Vashishtha M, Kielian M. Biochemical consequences of a mutation that controls the cholesterol dependence of Semliki Forest virus fusion. J Virol 2000; 74:1623-31. [PMID: 10644331 PMCID: PMC111636 DOI: 10.1128/jvi.74.4.1623-1631.2000] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The enveloped alphavirus Semliki Forest virus (SFV) infects cells via a low-pH-triggered membrane fusion reaction that requires cholesterol and sphingolipid in the target membrane. Cholesterol-depleted insect cells are highly resistant to alphavirus infection and were used to select srf-3, an SFV mutant that is approximately 100-fold less cholesterol dependent for infection due to a single amino acid change in the E1 spike subunit, proline 226 to serine. Sensitive lipid-mixing assays here demonstrated that the in vitro fusion of srf-3 and wild-type (wt) virus with cholesterol-containing liposomes had comparable kinetics, activation energies, and sphingolipid dependence. In contrast, srf-3 fusion with sterol-free liposomes was significantly more efficient than that of wt virus. Thus, the srf-3 mutation does not affect its general fusion properties with purified lipid bilayers but causes a marked and specific reduction in cholesterol dependence. Upon exposure to low pH, the E1 spike subunit undergoes distinct conformational changes, resulting in the exposure of an acid conformation-specific epitope and formation of an E1 homotrimer. These conformational changes were strongly cholesterol and sphingolipid dependent for wt SFV and strikingly less cholesterol dependent for srf-3. Our results thus demonstrate the functional importance of fusogenic E1 conformational changes in the control of SFV cholesterol dependence.
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Affiliation(s)
- P K Chatterjee
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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28
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Kielian M, Chatterjee PK, Gibbons DL, Lu YE. Specific roles for lipids in virus fusion and exit. Examples from the alphaviruses. Subcell Biochem 2000; 34:409-55. [PMID: 10808340 DOI: 10.1007/0-306-46824-7_11] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Affiliation(s)
- M Kielian
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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29
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Abstract
This chapter focuses on the work carried out with tick-borne encephalitis (TBE) virus, the structurally best characterized of the flaviviruses. The data is related to those obtained with other flaviviruses, which are assumed to have a conserved structural organization, and compare the characteristics of flavivirus fusion to those of other enveloped viruses. Fusion proteins from several different virus families, including Orthomyxoviridae , Paramyxoviridae , Retroviridae , and Filoviridae have been shown to exhibit striking structural similarities; they all use a common mechanism for inducing membrane fusion, and the same general model applies to all of these cases. The flavivirus genome is a positive-stranded RNA molecule consisting of a single, long open reading frame of more than 10,000 nucleotides flanked by noncoding regions at the 5′ and 3′ ends. The fusion properties of flaviviruses have been investigated using several different assay systems, including virus-induced cell–cell fusion and virus–liposome fusion. All of these studies indicate that flaviviruses require an acidic pH for fusion, consistent with their proposed mode of entry.
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Affiliation(s)
- F X Heinz
- Institute of Virology, University of Vienna, Austria
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30
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Ramstedt B, Leppimäki P, Axberg M, Slotte JP. Analysis of natural and synthetic sphingomyelins using high-performance thin-layer chromatography. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 266:997-1002. [PMID: 10583394 DOI: 10.1046/j.1432-1327.1999.00938.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The chromatographic behaviour of molecular species of sphingomyelin on HPTLC was investigated. Sphingomyelin gave a double band pattern on HPTLC plates developed using chloroform/methanol/acetic acid/water (25 : 15 : 4 : 2, v/v) or chloroform/methanol/water (25 : 10 : 1.1, v/v). HPTLC analysis of acyl chain-defined sphingomyelins showed that the Rf values increased linearly with the length of the N-linked acyl chain. A double-banded pattern was therefore seen for natural sphingomyelins with a bimodal fatty acid composition. Racemic sphingomyelins also gave a double band pattern on HPTLC, where the lower band represented the Derythro and the upper band the Lthreo isomer. We also showed that Derythro-N-16:0-dihydrosphingomyelin migrated faster on HPTLC than Derythro-N-16:0-sphingomyelin. The upper and lower band sphingomyelins from two different cell lines (human skin fibroblasts and baby hamster kidney cells) were separately scraped off the HPTLC plates and the fatty acid and long-chain base profiles were studied using GC-MS. The lower bands contained short-chain fatty acids and most of the fatty acids in the upper bands were long. The predominant long-chain base was sphingosine, which was found in both upper and lower bands, but sphinganine was found only in the upper bands. To conclude, there are at least three possible reasons for the sphingomyelin double bands on HPTLC; acyl chain length, long-chain base composition and stereochemistry. These reasons might sometimes overlap and, therefore, HPTLC alone is insufficient for complete analysis of the molecular species of sphingomyelin.
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Affiliation(s)
- B Ramstedt
- Department of Biochemistry, Abo Akademi University, Turku, Finland.
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31
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Smit JM, Bittman R, Wilschut J. Low-pH-dependent fusion of Sindbis virus with receptor-free cholesterol- and sphingolipid-containing liposomes. J Virol 1999; 73:8476-84. [PMID: 10482600 PMCID: PMC112867 DOI: 10.1128/jvi.73.10.8476-8484.1999] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
There is controversy as to whether the cell entry mechanism of Sindbis virus (SIN) involves direct fusion of the viral envelope with the plasma membrane at neutral pH or uptake by receptor-mediated endocytosis and subsequent low-pH-induced fusion from within acidic endosomes. Here, we studied the membrane fusion activity of SIN in a liposomal model system. Fusion was followed fluorometrically by monitoring the dilution of pyrene-labeled lipids from biosynthetically labeled virus into unlabeled liposomes or from labeled liposomes into unlabeled virus. Fusion was also assessed on the basis of degradation of the viral core protein by trypsin encapsulated in the liposomes. SIN fused efficiently with receptor-free liposomes, consisting of phospholipids and cholesterol, indicating that receptor interaction is not a mechanistic requirement for fusion of the virus. Fusion was optimal at pH 5.0, with a threshold at pH 6.0, and undetectable at neutral pH, supporting a cell entry mechanism of SIN involving fusion from within acidic endosomes. Under optimal conditions, 60 to 85% of the virus fused, depending on the assay used, corresponding to all of the virus bound to the liposomes as assessed in a direct binding assay. Preincubation of the virus alone at pH 5.0 resulted in a rapid loss of fusion capacity. Fusion of SIN required the presence of both cholesterol and sphingolipid in the target liposomes, cholesterol being primarily involved in low-pH-induced virus-liposome binding and the sphingolipid catalyzing the fusion process itself. Under low-pH conditions, the E2/E1 heterodimeric envelope glycoprotein of the virus dissociated, with formation of a trypsin-resistant E1 homotrimer, which kinetically preceded the fusion reaction, thus suggesting that the E1 trimer represents the fusion-active conformation of the viral spike.
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Affiliation(s)
- J M Smit
- University of Groningen, Department of Physiological Chemistry, 9713 AV Groningen, The Netherlands
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32
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Ramstedt B, Slotte JP. Comparison of the biophysical properties of racemic and d-erythro-N-acyl sphingomyelins. Biophys J 1999; 77:1498-506. [PMID: 10465760 PMCID: PMC1300437 DOI: 10.1016/s0006-3495(99)76997-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In this study stereochemically pure d-erythro-sphingomyelins (SMs) with either 16:0 or 18:1(cisDelta9) as the N-linked acyl-chain were synthesized. Our purpose was to examine the properties of these sphingomyelins and acyl-chain matched racemic (d-erythro/l-threo) sphingomyelins in model membranes. Liquid-expanded d-erythro-N-16:0-SM in monolayers was observed to pack more densely than the corresponding racemic sphingomyelin. Cholesterol desorption to beta-cyclodextrin was significantly slower from d-erythro-N-16:0-SM monolayers than from racemic N-16:0-SM monolayers. Significantly more condensed domains were seen in cholesterol/d-erythro-N-16:0-SM monolayers than in the corresponding racemic mixed monolayers, when [7-nitrobenz-2-oxa-1, 3-diazol-4-yl]phosphatidylcholine was used as a probe in monolayer fluorescence microscopy. With monolayers of N-18:1-SMs, both the lateral packing densities (sphingomyelin monolayers) and the rates of cholesterol desorption (mixed cholesterol/sphingomyelin monolayers) was found to be similar for d-erythro and racemic sphingomyelins. The phase transition temperature and enthalpy of d-erythro-N-16:0-SM in bilayer membranes were slightly higher compared with the corresponding racemic sphingomyelin (41.1 degrees C and 8.4 +/- 0.4 kJ/mol, and 39.9 degrees C and 7.2 +/- 0.2 kJ/mol, respectively). Finally, d-erythro-sphingomyelins in monolayers (both N-16:0 and N-18:1 species) were not as easily degraded at 37 degrees C by sphingomyelinase (Staphylococcus aureus) as the corresponding racemic sphingomyelins. We conclude that racemic sphingomyelins differ significantly in their biophysical properties from the physiologically relevant d-erythro sphingomyelins.
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Affiliation(s)
- B Ramstedt
- Department of Biochemistry and Pharmacy, Abo Akademi University, FIN 20521 Turku, Finland.
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33
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Gerasimov OV, Boomer JA, Qualls MM, Thompson DH. Cytosolic drug delivery using pH- and light-sensitive liposomes. Adv Drug Deliv Rev 1999; 38:317-338. [PMID: 10837763 DOI: 10.1016/s0169-409x(99)00035-6] [Citation(s) in RCA: 199] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A growing body of literature describes the development and applications of novel targeting and/or contents release triggering schemes to improve the therapeutic index of drugs encapsulated within liposomes. This review focuses on literature appearing between January 1995-December 1997 that report 1) antibody and receptor-mediated targeting approaches for improving drug localization and 2) acid, enzymatic, thermal or photochemical triggering processes that destabilize membranes and improve drug bioavailability via cytoplasmic delivery of liposomal contents.
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Affiliation(s)
- OV Gerasimov
- Department of Chemistry, Purdue University, West Lafayette, IN, USA
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34
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He L, Byun HS, Smit J, Wilschut J, Bittman R. Enantioselective Synthesis of a Novel Trans Double Bond Ceramide Analogue via Catalytic Asymmetric Dihydroxylation of an Enyne. The Role of the Trans Double Bond of Ceramide in the Fusion of Semliki Forest Virus with Target Membranes. J Am Chem Soc 1999. [DOI: 10.1021/ja981493z] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- LinLi He
- Contribution from the Department of Chemistry & Biochemistry, Queens College of The City University of New York, Flushing, New York 11367-1597, and Department of Physiological Chemistry, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Hoe-Sup Byun
- Contribution from the Department of Chemistry & Biochemistry, Queens College of The City University of New York, Flushing, New York 11367-1597, and Department of Physiological Chemistry, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Jolanda Smit
- Contribution from the Department of Chemistry & Biochemistry, Queens College of The City University of New York, Flushing, New York 11367-1597, and Department of Physiological Chemistry, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Jan Wilschut
- Contribution from the Department of Chemistry & Biochemistry, Queens College of The City University of New York, Flushing, New York 11367-1597, and Department of Physiological Chemistry, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Robert Bittman
- Contribution from the Department of Chemistry & Biochemistry, Queens College of The City University of New York, Flushing, New York 11367-1597, and Department of Physiological Chemistry, University of Groningen, 9713 AV Groningen, The Netherlands
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35
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Zitzer A, Zitzer O, Bhakdi S, Palmer M. Oligomerization of Vibrio cholerae cytolysin yields a pentameric pore and has a dual specificity for cholesterol and sphingolipids in the target membrane. J Biol Chem 1999; 274:1375-80. [PMID: 9880509 DOI: 10.1074/jbc.274.3.1375] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vibrio cholerae cytolysin permeabilizes animal cell membranes. Upon binding to the target lipid bilayer, the protein assembles into homo-oligomeric pores of an as yet unknown stoichiometry. Pore formation has been observed with model liposomes consisting of phosphatidylcholine and cholesterol, but the latter were much less susceptible to the cytolysin than were erythrocytes or intestinal epithelial cells. We here show that liposome permeabilization is strongly promoted if cholesterol is combined with sphingolipids, whereby the most pronounced effects are observed with monohexosylceramides and free ceramide. These two lipid species are prevalent in mammalian intestinal brush border membranes. We therefore propose that, on its natural target membranes, the cytolysin has a dual specificity for both cholesterol and ceramides. To assess the stoichiometry of the pore, we generated hybrid oligomers of two naturally occurring variants of the toxin that differ in molecular weight. On SDS-polyacrylamide gel electrophoresis, the mixed oligomers formed a pattern of six distinct bands. Ordered by decreasing electrophoretic mobility, the six oligomer species must comprise 0 to 5 subunits of the larger form; the pore thus is a pentamer. Due to both lipid specificity and pore stoichiometry, V. cholerae cytolysin represents a novel prototype in the class of bacterial pore-forming toxins.
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Affiliation(s)
- A Zitzer
- Institute of Medical Microbiology, University of Mainz, Augustusplatz, D55101 Germany
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36
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Abstract
The ability of viruses to transfer macromolecules between cells makes them attractive starting points for the design of biological delivery vehicles. Virus-based vectors and sub-viral systems are already finding biotechnological and medical applications for gene, peptide, vaccine and drug delivery. Progress has been made in understanding the cellular and molecular mechanisms underlying virus entry, particularly in identifying virus receptors. However, receptor binding is only a first step and we now have to understand how these molecules facilitate entry, how enveloped viruses fuse with cells or non-enveloped viruses penetrate the cell membrane, and what happens following penetration. Only through these detailed analyses will the full potential of viruses as vectors and delivery vehicles be realised. Here we discuss aspects of the entry mechanisms for several well-characterised viral systems. We do not attempt to provide a fully comprehensive review of virus entry but focus primarily on enveloped viruses.
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Affiliation(s)
| | | | - Mark Marsh
- Corresponding author. Tel.: +44 171 380 7807; fax: +44 171 380 7805; e-mail
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37
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Ulrich AS, Otter M, Glabe CG, Hoekstra D. Membrane fusion is induced by a distinct peptide sequence of the sea urchin fertilization protein bindin. J Biol Chem 1998; 273:16748-55. [PMID: 9642230 DOI: 10.1074/jbc.273.27.16748] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fertilization in the sea urchin is mediated by the membrane-associated acrosomal protein bindin, which plays a key role in the adhesion and fusion between sperm and egg. We have investigated the structure/function relationship of an 18-amino acid peptide fragment "B18," which represents the minimal membrane binding motif of the protein and resembles a putative fusion peptide. The peptide was found to mimic the behavior of its parent protein bindin with respect to (a) its high affinity for lipid bilayers, (b) the ability to aggregate and fuse vesicles, (c) the binding of Zn2+ by a histidine-rich motif, (d) the tendency to self-assemble, and (e), as indicated earlier, the adhesion to cell surface polysaccharides. Fluorescence and light scattering assays were used here to monitor peptide-induced lipid mixing, leakage, and aggregation of large unilamellar sphingomyelin/cholesterol vesicles. For these activities, B18 requires the presence of Zn2+ ions, with which it forms oligomeric complexes and assumes a partially alpha-helical conformation, as observed by circular dichroism. We conclude that aggregation and fusion involves a "trans-complex" between peptides on apposing vesicles that are connected by Zn2+ bridges.
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Affiliation(s)
- A S Ulrich
- Institute of Molecular Biology, University of Jena, Winzerlaer Strasse 10, 07745 Jena, Germany
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38
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Ruiz-Argüello MB, Goñi FM, Pereira FB, Nieva JL. Phosphatidylinositol-dependent membrane fusion induced by a putative fusogenic sequence of Ebola virus. J Virol 1998; 72:1775-81. [PMID: 9499027 PMCID: PMC109466 DOI: 10.1128/jvi.72.3.1775-1781.1998] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The membrane-interacting abilities of three sequences representing the putative fusogenic subdomain of the Ebola virus transmembrane protein have been investigated. In the presence of calcium, the sequence EBO(GE) (GAAIGLAWIPYFGPAAE) efficiently fused unilamellar vesicles composed of phosphatidylcholine, phosphatidylethanolamine, cholesterol, and phosphatidylinositol (molar ratio, 2:1:1:0.5), a mixture that roughly resembles the lipid composition of the hepatocyte plasma membrane. Analysis of the lipid dependence of the process demonstrated that the fusion activity of EBO(GE) was promoted by phosphatidylinositol but not by other acidic phospholipids. In comparison, EBO(EA) (EGAAIGLAWIPYFGPAA) and EBO(EE) (EGAAIGLAWIPYFGPAAE) sequences, which are similar to EBO(GE) except that they bear the negatively charged glutamate residue at the N terminus and at both the N and C termini, respectively, induced fusion to a lesser extent. As revealed by binding experiments, the glutamate residue at the N terminus severely impaired peptide-vesicle interaction. In addition, the fusion-competent EBO(GE) sequence did not associate significantly with vesicles lacking phosphatidylinositol. Tryptophan fluorescence quenching by vesicles containing brominated phospholipids indicated that the EBO(GE) peptide penetrated to the acyl chain level only when the membranes contained phosphatidylinositol. We conclude that binding and further penetration of the Ebola virus putative fusion peptide into membranes might be governed by the nature of the N-terminal residue and by the presence of phosphatidylinositol in the target membrane. Moreover, since insertion of such a peptide leads to membrane destabilization and fusion, the present data would be compatible with the involvement of this sequence in Ebola virus fusion.
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Affiliation(s)
- M B Ruiz-Argüello
- Grupo de Biomembranas (Unidad Asociada al CSIC), Departamento de Bioquímica, Universidad del Pais Vasco, Bilbao, Spain
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39
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Vashishtha M, Phalen T, Marquardt MT, Ryu JS, Ng AC, Kielian M. A single point mutation controls the cholesterol dependence of Semliki Forest virus entry and exit. J Cell Biol 1998; 140:91-9. [PMID: 9425157 PMCID: PMC2132589 DOI: 10.1083/jcb.140.1.91] [Citation(s) in RCA: 121] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/1997] [Revised: 10/08/1997] [Indexed: 02/05/2023] Open
Abstract
Membrane fusion and budding are key steps in the life cycle of all enveloped viruses. Semliki Forest virus (SFV) is an enveloped alphavirus that requires cellular membrane cholesterol for both membrane fusion and efficient exit of progeny virus from infected cells. We selected an SFV mutant, srf-3, that was strikingly independent of cholesterol for growth. This phenotype was conferred by a single amino acid change in the E1 spike protein subunit, proline 226 to serine, that increased the cholesterol independence of both srf-3 fusion and exit. The srf-3 mutant emphasizes the relationship between the role of cholesterol in membrane fusion and virus exit, and most significantly, identifies a novel spike protein region involved in the virus cholesterol requirement.
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Affiliation(s)
- M Vashishtha
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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40
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Corver J, Bron R, Snippe H, Kraaijeveld C, Wilschut J. Membrane fusion activity of Semliki Forest virus in a liposomal model system: specific inhibition by Zn2+ ions. Virology 1997; 238:14-21. [PMID: 9375004 DOI: 10.1006/viro.1997.8799] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Semliki Forest virus (SFV) has been shown previously to fuse efficiently with cholesterol- and sphingolipid-containing liposomal model membranes in a low-pH-dependent manner. Several steps can be distinguished in this process, including low-pH-induced irreversible binding of the virus to the liposomes, facilitated by target membrane cholesterol, and subsequent fusion of the viral membrane with the liposomal bilayer, specifically catalyzed by target membrane sphingolipid. Binding and fusion are mediated by the heterodimeric viral envelope glycoprotein E2/E1. At low pH the heterodimer dissociates, and the E1 monomers convert to a homotrimeric structure, the presumed fusion-active conformation of the viral spike. In this paper, we demonstrate that SFV-liposome fusion is specifically inhibited by Zn2+ ions. The inhibition is at the level of the fusion reaction itself, since virus-liposome binding was found to be unaffected. Zn2+ did not inhibit E2/E1 dissociation, but severely inhibited exposure of an acid-specific epitope on E1, E1 homotrimer formation, and acquisition of trypsin-resistance. It is concluded that virus--liposome binding solely requires low-pH-induced E2/E1 heterodimer dissociation, while fusion depends on further rearrangements in the E1 spike protein. As these rearrangements occur subsequent to the binding step, their precise course, including the formation of a fusion complex, may be influenced by interaction of E1 with target membrane lipids.
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Affiliation(s)
- J Corver
- Department of Physiological Chemistry, GUIDE, University of Groningen, The Netherlands
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41
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Lange S, Nüssler F, Kauschke E, Lutsch G, Cooper EL, Herrmann A. Interaction of earthworm hemolysin with lipid membranes requires sphingolipids. J Biol Chem 1997; 272:20884-92. [PMID: 9252415 DOI: 10.1074/jbc.272.33.20884] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Lytic activity in the coelomic fluid of earthworm (Eisenia fetida fetida) has been ascribed to eiseniapore, a hemolytic protein of 38 kDa. Since receptors for eiseniapore on target cell membranes are not known, we used lipid vesicles of various composition to determine whether specific lipids may serve as receptors. Lytic activity of eiseniapore was probed by the relief of fluorescence dequenching from the fluorophore 8-aminonaphthalene-1,3, 6-trisulfonic acid originally incorporated into the vesicle lumen as a complex with p-xylene-bis-pyridinium bromide. Hemolysin binds to and disturbs the lipid bilayer only when distinct sphingolipids consisting of a hydrophilic head group as phosphorylcholine or galactosyl as well as the ceramide backbone, e.g. sphingomyelin, are present. Cholesterol enhances eiseniapore lytic activity toward sphingomyelin-containing vesicles probably due to interaction with sphingomyelin. Leakage of vesicles was most efficient when the lipid composition resembled that of the outer leaflet of human erythrocytes. Presumably, an oligomeric protein pore formed by six monomers is responsible for leakage of sphingomyelin-containing vesicles. The secondary structure of eiseniapore did not change upon binding to lipid membranes. The lytic activity of eiseniapore was completely abolished after its denaturation or after preincubation with polyclonal antibodies. Our results suggest that the presence of specific sphingolipids is sufficient to mediate lytic activity of eiseniapore. This action contributes to our understanding of earthworm immune responses.
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Affiliation(s)
- S Lange
- Universität Greifswald, Zoologisches Institut und Museum, Bachstrasse 11/12, D-17489 Greifswald, Federal Republic of Germany
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42
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Abstract
Significant progress has been made in elucidating the mechanisms of viral membrane fusion proteins; both those that function at low, as well as those that function at neutral, pH. For many viral fusion proteins evidence now suggests that a triggered conformational change that exposes a previously cryptic fusion peptide, along with a rearrangement of the fusion protein oligomer, allows the fusion peptide to gain access to the target bilayer and thus initiate the fusion reaction. Although the topologically equivalent process of cell-cell fusion is less well understood, several cell surface proteins, including members of the newly described ADAM gene family, have emerged as candidate adhesion/fusion proteins.
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Affiliation(s)
- L D Hernandez
- Department of Cell Biology, University of Virginia, Charlottesville 22908, USA
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43
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Ruiz-Argüello MB, Basáñez G, Goñi FM, Alonso A. Different effects of enzyme-generated ceramides and diacylglycerols in phospholipid membrane fusion and leakage. J Biol Chem 1996; 271:26616-21. [PMID: 8900135 DOI: 10.1074/jbc.271.43.26616] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
When large unilamellar vesicles consisting of sphingomyelin:phosphatidylethanolamine:cholesterol (2:1:1 molar ratio) are treated with sphingomyelinase, production of ceramides in the bilayer is accompanied by leakage of vesicle aqueous contents and by vesicle aggregation in the absence of lipid mixing or vesicle fusion. This is in contrast to the situation of phosphatidylcholine:phosphatidylethanolamine:cholesterol (2:1:1 molar ratio) liposomes when treated with phospholipase C. In that case, in situ generation of diacylglycerol leads to vesicle aggregation followed by vesicle fusion in the absence of leakage (Nieva, J. L., Goñi, F. M., and Alonso, A. (1989) Biochemistry 28, 7364-7367). Moreover, when ceramides (5-10 mol %) are included in the formulation of the phosphatidylcholine-containing vesicles, they reduce the lag time of phospholipase C-induced fusion, although they are less active than diacylglycerols in this respect. 31P NMR studies of aqueous lipid dispersions show that diacylglycerols as well as ceramides induce a thermotropic lamellar to non-lamellar phase transition in both phospholipid:cholesterol mixtures under study although sphingomyelin-containing bilayers are more stable than those containing phosphatidylcholine, and ceramide is less active than diacylglycerol in promoting non-lamellar phase formation. These observations are relevant to both the physiological role of ceramides and the current views on the mechanism of membrane fusion.
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Affiliation(s)
- M B Ruiz-Argüello
- Grupo Biomembranas (Unidad Asociada al Cosejo Superior de Investigaciones Ciéntifícas), Departamento de Bioquímica, Universidad del País Vasco, Apartado 644, 48080 Bilbao, Spain
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