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Rice A, Zimmerberg J, Pastor RW. Initiation and evolution of pores formed by influenza fusion peptides probed by lysolipid inclusion. Biophys J 2023; 122:1018-1032. [PMID: 36575795 PMCID: PMC10111278 DOI: 10.1016/j.bpj.2022.12.029] [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] [Received: 10/18/2022] [Revised: 12/09/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022] Open
Abstract
The fusion peptide (FP) domain is necessary for the fusogenic activity of spike proteins in a variety of enveloped viruses, allowing the virus to infect the host cell, and is the only part of the protein that interacts directly with the target membrane lipid tails during fusion. There are consistent findings of poration by this domain in experimental model membrane systems, and, in certain conditions, the isolated FPs can generate pores. Here, we use molecular dynamics simulations to investigate the specifics of how these FP-induced pores form in membranes with different compositions of lysolipid and POPC. The simulations show that pores form spontaneously at high lysolipid concentrations via hybrid intermediates, where FP aggregates in the cis leaflet tilt to form a funnel-like structure that spans the leaflet and locally reduces the hydrophobic thickness that must be traversed by water to form a pore. By restraining a single FP within an FP aggregate to this tilted conformation, pores can be formed in lower-lysolipid-content membranes, including pure POPC, on the 100-ns timescale, much more rapidly than in unbiased simulations in bilayers with the same composition. The pore formation pathway is similar to the spontaneous formation in high lysolipid concentrations. Depending on the membrane composition, the pores can be metastable (as seen in POPC) or lead to membrane rupture.
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Affiliation(s)
- Amy Rice
- Laboratory of Computational Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Joshua Zimmerberg
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland.
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2
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Rice A, Haldar S, Wang E, Blank PS, Akimov SA, Galimzyanov TR, Pastor RW, Zimmerberg J. Planar aggregation of the influenza viral fusion peptide alters membrane structure and hydration, promoting poration. Nat Commun 2022; 13:7336. [PMID: 36470871 PMCID: PMC9722698 DOI: 10.1038/s41467-022-34576-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 10/28/2022] [Indexed: 12/07/2022] Open
Abstract
To infect, enveloped viruses employ spike protein, spearheaded by its amphipathic fusion peptide (FP), that upon activation extends out from the viral surface to embed into the target cellular membrane. Here we report that synthesized influenza virus FPs are membrane active, generating pores in giant unilamellar vesicles (GUV), and thus potentially explain both influenza virus' hemolytic activity and the liposome poration seen in cryo-electron tomography. Experimentally, FPs are heterogeneously distributed on the GUV at the time of poration. Consistent with this heterogeneous distribution, molecular dynamics (MD) simulations of asymmetric bilayers with different numbers of FPs in one leaflet show FP aggregation. At the center of FP aggregates, a profound change in the membrane structure results in thinning, higher water permeability, and curvature. Ultimately, a hybrid bilayer nanodomain forms with one lipidic leaflet and one peptidic leaflet. Membrane elastic theory predicts a reduced barrier to water pore formation when even a dimer of FPs thins the membrane as above, and the FPs of that dimer tilt, to continue the leaflet bending initiated by the hydrophobic mismatch between the FP dimer and the surrounding lipid.
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Affiliation(s)
- Amy Rice
- grid.94365.3d0000 0001 2297 5165Laboratory of Computational Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD USA
| | - Sourav Haldar
- grid.94365.3d0000 0001 2297 5165Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD USA ,grid.418363.b0000 0004 0506 6543Present Address: Division of Virus Research and Therapeutics, CSIR-Central Drug Research Institute, Lucknow, UP India
| | - Eric Wang
- grid.94365.3d0000 0001 2297 5165Laboratory of Computational Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD USA ,grid.94365.3d0000 0001 2297 5165Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD USA
| | - Paul S. Blank
- grid.94365.3d0000 0001 2297 5165Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD USA
| | - Sergey A. Akimov
- grid.4886.20000 0001 2192 9124A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia
| | - Timur R. Galimzyanov
- grid.4886.20000 0001 2192 9124A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, Russia ,grid.35043.310000 0001 0010 3972National University of Science and Technology “MISiS”, 4 Leninskiy Prospect, Moscow, Russia
| | - Richard W. Pastor
- grid.94365.3d0000 0001 2297 5165Laboratory of Computational Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD USA
| | - Joshua Zimmerberg
- grid.94365.3d0000 0001 2297 5165Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD USA
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3
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Düzgüneş N, Fernandez-Fuentes N, Konopka K. Inhibition of Viral Membrane Fusion by Peptides and Approaches to Peptide Design. Pathogens 2021; 10:1599. [PMID: 34959554 PMCID: PMC8709411 DOI: 10.3390/pathogens10121599] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 12/06/2021] [Accepted: 12/06/2021] [Indexed: 12/29/2022] Open
Abstract
Fusion of lipid-enveloped viruses with the cellular plasma membrane or the endosome membrane is mediated by viral envelope proteins that undergo large conformational changes following binding to receptors. The HIV-1 fusion protein gp41 undergoes a transition into a "six-helix bundle" after binding of the surface protein gp120 to the CD4 receptor and a co-receptor. Synthetic peptides that mimic part of this structure interfere with the formation of the helix structure and inhibit membrane fusion. This approach also works with the S spike protein of SARS-CoV-2. Here we review the peptide inhibitors of membrane fusion involved in infection by influenza virus, HIV-1, MERS and SARS coronaviruses, hepatitis viruses, paramyxoviruses, flaviviruses, herpesviruses and filoviruses. We also describe recent computational methods used for the identification of peptide sequences that can interact strongly with protein interfaces, with special emphasis on SARS-CoV-2, using the PePI-Covid19 database.
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Affiliation(s)
- Nejat Düzgüneş
- Department of Biomedical Sciences, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, CA 94103, USA;
| | - Narcis Fernandez-Fuentes
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth SY23 3EE, UK;
| | - Krystyna Konopka
- Department of Biomedical Sciences, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, CA 94103, USA;
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4
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Rathore SS, Liu Y, Yu H, Wan C, Lee M, Yin Q, Stowell MHB, Shen J. Intracellular Vesicle Fusion Requires a Membrane-Destabilizing Peptide Located at the Juxtamembrane Region of the v-SNARE. Cell Rep 2019; 29:4583-4592.e3. [PMID: 31875562 PMCID: PMC6990648 DOI: 10.1016/j.celrep.2019.11.107] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/13/2019] [Accepted: 11/26/2019] [Indexed: 12/11/2022] Open
Abstract
Intracellular vesicle fusion is mediated by soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) and Sec1/Munc18 (SM) proteins. It is generally accepted that membrane fusion occurs when the vesicle and target membranes are brought into close proximity by SNAREs and SM proteins. In this work, we demonstrate that, for fusion to occur, membrane bilayers must be destabilized by a conserved membrane-embedded motif located at the juxtamembrane region of the vesicle-anchored v-SNARE. Comprised of basic and hydrophobic residues, the juxtamembrane motif perturbs the lipid bilayer structure and promotes SNARE-SM-mediated membrane fusion. The juxtamembrane motif can be functionally substituted with an unrelated membrane-disrupting peptide in the membrane fusion reaction. These findings establish the juxtamembrane motif of the v-SNARE as a membrane-destabilizing peptide. Requirement of membrane-destabilizing peptides is likely a common feature of biological membrane fusion.
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Affiliation(s)
- Shailendra S Rathore
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA
| | - Yinghui Liu
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA; Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Haijia Yu
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA; Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China.
| | - Chun Wan
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA
| | - MyeongSeon Lee
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA
| | - Qian Yin
- Department of Biological Sciences and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
| | - Michael H B Stowell
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA
| | - Jingshi Shen
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA.
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5
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Delgado CL, Núñez E, Yélamos B, Gómez-Gutiérrez J, Peterson DL, Gavilanes F. Spectroscopic Characterization and Fusogenic Properties of PreS Domains of Duck Hepatitis B Virus. Biochemistry 2012; 51:8444-54. [DOI: 10.1021/bi3008406] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Carmen L. Delgado
- Departamento de Bioquímica
y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid 28040, Spain
| | - Elena Núñez
- Departamento de Bioquímica
y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid 28040, Spain
| | - Belén Yélamos
- Departamento de Bioquímica
y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid 28040, Spain
| | - Julián Gómez-Gutiérrez
- Departamento de Bioquímica
y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid 28040, Spain
| | - Darrell L. Peterson
- Department of Biochemistry and
Molecular Biology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298, United
States
| | - Francisco Gavilanes
- Departamento de Bioquímica
y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid 28040, Spain
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6
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Ge M, Freed JH. Fusion peptide from influenza hemagglutinin increases membrane surface order: an electron-spin resonance study. Biophys J 2009; 96:4925-34. [PMID: 19527651 DOI: 10.1016/j.bpj.2009.04.015] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 02/27/2009] [Accepted: 04/06/2009] [Indexed: 11/29/2022] Open
Abstract
A spin-labeling study of interactions of a fusion peptide from the hemagglutinin of the influenza virus, wt20, and a fusion-inactive mutant DeltaG1 with dimyristoylphosphatidylcholine (DMPC) and 1-palmitoyl-2-oleoyl-phosphatdylcholine bilayers was performed. We found that upon binding of wt20, the ordering of headgroups and the ordering of acyl chains near the headgroup increased significantly, in a manner consistent with a cooperative phenomenon. However, changes in the order at the end of the acyl chains were negligible. The ordering effect of wt20 on the headgroup was much stronger at pH 5 than at pH 7. No effect of DeltaG1 binding on the order of bilayers was evident. We also found that 1-palmitoyl-2-hydroxyl phosphatidylcholine, a membrane-fusion inhibitor, decreased the ordering of DMPC headgroups, whereas arachidonic acid, a membrane-fusion promoter, increased the ordering of DMPC headgroups. These results suggest that increases in headgroup ordering may be important for membrane fusion. We propose that upon binding of wt20, which is known to affect only the outer leaflet of the bilayer, this outer leaflet becomes more ordered, and thus more solid-like. Then the coupling between the hardened outer leaflet and the softer inner leaflet generates bending stresses in the bilayer, which tend to increase the negative curvature of the bilayer. We suggest that the increased ordering in the headgroup region enhances dipolar interactions and lowers electrostatic energy, which may provide an energy source for membrane fusion. Possible roles of bending stresses in promoting membrane fusion are discussed.
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Affiliation(s)
- Mingtao Ge
- National Biomedical Center for Advanced ESR Technology, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 15853, USA
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7
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8
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Lorin A, Lins L, Stroobant V, Brasseur R, Charloteaux B. The minimal fusion peptide of simian immunodeficiency virus corresponds to the 11 first residues of gp32. J Pept Sci 2007; 14:423-8. [DOI: 10.1002/psc.949] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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9
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Pacheco B, Gómez-Gutiérrez J, Yélamos B, Delgado C, Roncal F, Albar JP, Peterson D, Gavilanes F. Membrane-perturbing properties of three peptides corresponding to the ectodomain of hepatitis C virus E2 envelope protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:755-63. [PMID: 16777058 DOI: 10.1016/j.bbamem.2006.04.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Revised: 03/31/2006] [Accepted: 04/24/2006] [Indexed: 10/24/2022]
Abstract
Based on the predicted capacity to interact with membranes at the interface, we have found three regions in the ectodomain of the hepatitis C virus envelope glycoprotein E2 (430-449, 543-560 and 603-624) with the ability to destabilize membranes. Three peptides corresponding to the sequence of these regions have been synthesized and their interaction with liposomes have been characterized. The three peptides were able to insert deeply into the hydrophobic core of negatively charged phospholipids as stated by fluorescence depolarization of the probe 1,6-diphenyl-1,3,5-hexatriene. Peptides E2(430-449) and E2(603-624) were able to induce aggregation of phosphatidylglycerol vesicles in a concentration-dependent manner both at neutral and acidic pH while peptide E2(543-560) did not induce any increase of optical density at 360 nm in the concentration range studied. The three peptides induced lipid mixing and the release of the internal contents in a dose-dependent manner when acidic phospholipids were used. Fourier transformed infrared spectroscopy indicated that the peptides adopted mainly a beta-sheet conformation which is not modified by the presence of acidic phospholipids. Taken together, our results point out to the involvement of these three regions in the fusion mechanism of HCV at the plasma membrane level.
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Affiliation(s)
- Beatriz Pacheco
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain
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10
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Nieva JL, Agirre A. Are fusion peptides a good model to study viral cell fusion? BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1614:104-15. [PMID: 12873771 DOI: 10.1016/s0005-2736(03)00168-8] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Fusion peptides are hydrophobic and conserved sequences located within glycoprotein ectodomains that protrude from the virion surface. Direct participation of fusion peptides in the viral membrane fusion phenomenon has been inferred from genetic analyses showing that even a single residue substitution or a deletion within these sequences may completely block the process. However, the specific fusion peptide activities associated to the multi-step fusion mechanism are not well defined. Based on the assumption that fusion peptides are transferred into target membranes, biophysical methodologies have been applied to study integration into model membranes of synthetic fragments representing functional and non-functional sequences. From these studies, it is inferred that, following insertion, functional sequences generate target membrane perturbations and adopt specific structural arrangements within. Further characterization of these artificial systems may help in understanding the molecular processes that bring initial bilayer destabilizations to the eventual opening of a fusion pore.
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Affiliation(s)
- José L Nieva
- Unidad de Biofísica (CSIC-UPV/EHU) and Departamento de Bioquímica, Universidad del País Vasco, Aptdo. 644, 48080, Bilbao, Spain.
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11
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Bertocco A, Formaggio F, Toniolo C, Broxterman QB, Epand RF, Epand RM. Design and function of a conformationally restricted analog of the influenza virus fusion peptide. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 2003; 62:19-26. [PMID: 12787447 DOI: 10.1034/j.1399-3011.2003.00063.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A conformationally restricted analog of the N-terminal 12-residue peptide segment of the HA2 subunit of the PPV/34, PR/8/34, and Jap/57 strains of influenza virus hemagglutinin was synthesized containing three residues of Calpha-methyl-valine. This peptide has a higher content of helical structure in the presence of 50% trifluoroethanol or when interacting with liposomes of egg phosphatidylcholine compared with the conformationally more flexible control peptide with the native sequence. The control and analog peptides had opposite effects on membrane curvature as measured by shifts in the bilayer-to-hexagonal phase transition temperature of a synthetic phosphatidylethanolamine derivative. The control peptide promoted more negative curvature, particularly at acidic pH and was also more potent than the analog in promoting lipid mixing. The results indicate that the ability of the peptide to sample a broader range of conformations is required for the influenza fusion peptide to destabilize membranes and that a rigid helical structure is less fusogenic. The difference between the two peptides and between pH 7.4 and pH 5.0 show a correlation between the ability to promote negative curvature and to accelerate lipid mixing.
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Affiliation(s)
- A Bertocco
- Institute of Biomolecular Chemistry, CNR, Department of Organic Chemistry, University of Padova, 35131 Padova, Italy
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12
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Affiliation(s)
- Nejat Düzgüneş
- Department of Microbiology, School of Dentistry, University of the Pacific, 2155 Webster Street, San Francisco, California 94115, USA
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13
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Affiliation(s)
- Pierre Bonnafous
- Crucell Holland BV, Archimedesweg 4, P.O. Box 2048, Leiden, The Netherlands
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14
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Brandenburg K, Harris F, Dennison S, Seydel U, Phoenix D. Domain V of m-calpain shows the potential to form an oblique-orientated alpha-helix, which may modulate the enzyme's activity via interactions with anionic lipid. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:5414-22. [PMID: 12423339 DOI: 10.1046/j.1432-1033.2002.03225.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The activity of m-calpain, a heterodimeric, Ca2+-dependent cysteine protease appears to be modulated by membrane interactions involving oblique-orientated alpha-helix formation by a segment, GTAMRILGGVI, in the protein's smaller subunit. Here, graphical and hydrophobic moment-based analyses predicted that this segment may form an alpha-helix with strong structural resemblance to the influenza virus peptide, HA2, a known oblique-orientated alpha-helix former. Fourier transform infrared spectroscopy showed that a peptide homologue of the GTAMRILGGVI segment, VP1, adopted low levels of alpha-helical structure ( approximately 20%) in the presence of zwitterionic lipid and induced a minor decrease (3 degrees C) in the gel to liquid-crystalline phase transition temperature, TC, of the hydrocarbon chains of zwitterionic membranes, suggesting interaction with the lipid headgroup region. In contrast, VP1 adopted high levels of alpha-helical structure (65%) in the presence of anionic lipid, induced a large increase (10 degrees C) in the TC of anionic membranes, and showed high levels of anionic lipid monolayer penetration (DeltaSP = 5.5 mN.m-1), suggesting deep levels of membrane penetration. VP1 showed strong haemolytic ability (LD50 = 1.45 mm), but in the presence of ionic agents, this ability, and that of VP1 to penetrate anionic lipid monolayers, was greatly reduced. In combination, our results suggest that m-calpain domain V may penetrate membranes via the adoption of an oblique-orientated alpha-helix and electrostatic interactions. We speculate that these interactions may involve snorkelling by an arginine residue located in the polar face of this alpha-helix.
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15
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Mastrobattista E, Koning GA, van Bloois L, Filipe ACS, Jiskoot W, Storm G. Functional characterization of an endosome-disruptive peptide and its application in cytosolic delivery of immunoliposome-entrapped proteins. J Biol Chem 2002; 277:27135-43. [PMID: 12021269 DOI: 10.1074/jbc.m200429200] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antibody-directed liposomes (immunoliposomes) are frequently used for targeted drug delivery. However, delivery of large biotherapeutic molecules (i.e. peptides, proteins, or nucleic acids) with immunoliposomes is often hampered by an inefficient cytosolic release of entrapped macromolecules after target cell binding and subsequent endocytosis of immunoliposomes. To enhance cytosolic drug delivery from immunoliposomes present inside endosomes, a pH-dependent fusogenic peptide (diINF-7) resembling the NH(2)-terminal domain of influenza virus hemagglutinin HA-2 subunit was used. Functional characterization of this dimeric peptide showed its ability to induce fusion between liposome membranes and leakage of liposome-entrapped compounds when exposed to low pH. In a second series of experiments, diINF-7 peptides were encapsulated in immunoliposomes to enhance the endosomal escape of diphtheria toxin A chain (DTA), which inhibits protein synthesis when delivered into the cytosol of target cells. Immunoliposomes targeted to the internalizing epidermal growth factor receptor on the surface of ovarian carcinoma cells (OVCAR-3) and containing encapsulated DTA did not show any cytotoxicity toward OVCAR-3 cells. Cytotoxicity was only observed when diINF-7 peptides and DTA were co-encapsulated in the immunoliposomes. Thus, diINF-7 peptides entrapped inside liposomes can greatly enhance cytosolic delivery of liposomal macromolecules by pH-dependent destabilization of endosomal membranes after cellular uptake of liposomes.
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Affiliation(s)
- Enrico Mastrobattista
- Department of Pharmaceutics, Utrecht University, P.O. Box 80 082, Utrecht 3508 TB, The Netherlands
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16
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Egashira M, Gorbenko G, Tanaka M, Saito H, Molotkovsky J, Nakano M, Handa T. Cholesterol modulates interaction between an amphipathic class A peptide, Ac-18A-NH2, and phosphatidylcholine bilayers. Biochemistry 2002; 41:4165-72. [PMID: 11900560 DOI: 10.1021/bi011885+] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cholesterol (Chol) in phosphatidylcholine large unilamellar vesicles (PC LUV) modulated interaction of the bilayers with a class A amphipathic peptide, Ac-18A-NH2: Chol increased the peptide binding capacity and reduced the affinity together with the peptide-induced leakage of calcein from LUV. Similar effects of Chol have been observed on the interaction of LUV with apoA-I [Saito, H., Miyako, Y., Handa, T., and Miyajima, K. (1997) J. Lipid Res. 38, 287-294]. Circular dichroism (CD) spectra of the peptide indicated a similar helical structure formation in LUV with and without Chol. The fluorescence spectral shift, quantum yield, anisotropy, and acrylamide-quenching of the peptide Trp indicated that in PC:Chol (3:2) LUV, Ac-18A-NH2 was located in a more polar membrane environment with increased motional freedom and greater accessibility to the aqueous medium. Fluorescence energy transfer from the Trp indole ring to acceptors situated at different depths in the bilayers revealed that the amphipathic peptide penetrated the hydrophobic interior of PC bilayers, while the peptide was located at the polar zwitterionic surface in PC:Chol LUV. The inclusion of Chol causes the headgroup separation of PC at the surface of LUV and increases the binding maximum of the wedge-shaped amphipathic peptide without disrupting the membrane structure. In addition, the rigidifying effect of Chol on PC acyl chains prevents the penetration of the peptide into the bilayer interior. These findings imply that Chol in membranes affects the binding and motional freedom of exchangeable plasma apolipoproteins containing class A amphipathic sequences, e.g., apoA-I and apoCs.
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Affiliation(s)
- Masashi Egashira
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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17
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Mastrobattista E, Crommelin DJA, Wilschut J, Storm G. Targeted liposomes for delivery of protein-based drugs into the cytoplasm of tumor cells. J Liposome Res 2002; 12:57-65. [PMID: 12604039 DOI: 10.1081/lpr-120004777] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Our goal was to deliver therapeutically active macromolecules into the cytosol of target cells. First, attempts were made to prepare virosomes that specifically interact with OVCAR-3 cells (human ovarian cancer cells). Detergent solubilized influenza virus envelopes were reconstituted forming virosomes. Cell specificity was introduced by incorporating PEG-derivatized lipids with mAB 323/A3 (Fab' fragments) connected to their distal PEG end. These cell-specific, modified virosomes maintained their fusogenic activity when lowering the pH. Most importantly, antibody-mediated binding was a prerequisite for low-pH induced membrane fusion. However, basically, there are two problems with this approach: (1) these virosomes are quite leaky and (2) virosomes can be expected to be immunogenic. A solution to tackle leakage and potential immunogenicity of these site-specific liposomal structures is to use immuno-PEG-liposomes with a pH-dependent fusogen inside the liposome. The system that we designed to test this concept consisted of (1) the fusogenic di-peptide dINF-7, (2) the monoclonal antibody 425 connected to the distal end of PEG-PE (for site specific binding and endosomal uptake), (3) diphtheria toxin chain A (DTA, as carrier-dependent active compound) and phosphatidylcholine/cholesterol as 'bilayer backbone'. A series of tests were performed to show that selective binding and pH-dependent destabilization of (endosomal) membranes indeed occurred. To test the cytotoxic activity of these DTA loaded liposomes, OVCAR-3 cells were used for testing. OVCAR-3 cells express the epidermal growth factor receptor, which is the ligand for antibody 425. In vitro, these site specific and fusogenic liposomes showed a remarkable, cell specific cytotoxic effect.
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Affiliation(s)
- Enrico Mastrobattista
- Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands
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18
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Fischer PM, Krausz E, Lane DP. Cellular delivery of impermeable effector molecules in the form of conjugates with peptides capable of mediating membrane translocation. Bioconjug Chem 2001; 12:825-41. [PMID: 11716670 DOI: 10.1021/bc0155115] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Most molecules that are not actively imported by living cells are impermeable to cell membranes, including practically all macromolecules and even many small molecules whose physicochemical properties prevent passive membrane diffusion. The use of peptide vectors capable of transporting such molecules into cells in the form of covalent conjugates has become an increasingly attractive solution to this problem. Not only has this technology permitted the study of modulating intracellular target proteins, but it has also gained importance as an alternative to conventional cellular transfection with oligonucleotides. Peptide vectors derived from viral, bacterial, insect, and mammalian proteins endowed with membrane translocation properties have now been proposed as delivery vectors. These are discussed comprehensively and critically in terms of relative utility, applications to compound classes and specific molecules, and relevant conjugation chemistry. Although in most cases the mechanisms of membrane translocation are still unclear, physicochemical studies have been carried out with a number of peptide delivery vectors. Unifying and distinguishing mechanistic features of the various vectors are discussed. Until a few years ago speculations that it might be possible to deliver peptides, proteins, oligonucleotides, and impermeable small molecules with the aid of cellular delivery peptides not only to target cells in vitro, but in vivo, was received with scepticism. However, the first studies showing pharmacological applications of conjugates between macromolecules and peptide delivery vectors are now being reported, and therapies based on such conjugates are beginning to appear feasible.
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Affiliation(s)
- P M Fischer
- Cyclacel Limited, Dundee Technopole, James Lindsay Place, Dundee DD1 5JJ, Scotland, UK.
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19
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Samuel O, Shai Y. Participation of two fusion peptides in measles virus-induced membrane fusion: emerging similarity with other paramyxoviruses. Biochemistry 2001; 40:1340-9. [PMID: 11170461 DOI: 10.1021/bi001533n] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Paramyxoviruses penetrate into their host cells by fusing their membranes with the plasma membrane. The hydrophobic N terminus of their F1 protein, termed the 'fusion peptide', is thought to be responsible for this process. Recently, an additional internal fusion peptide, homologous in sequence to the N-terminal fusion peptide of HIV-1, was identified in the Sendai virus F1 protein. Here, we investigated whether the presence of an additional internal fusion peptide is a general feature of paramyxoviridae. To this end, we synthesized and structurally and functionally characterized three peptides: (i) MV-197, which corresponds to an internal segment of the F1 protein of the measles virus (amino acids 197-225), homologous in location but not in sequence to the internal fusion peptide of the Sendai virus, (ii) Mu-MV-197, a randomized version of MV-197, and (iii) the 33 amino acid N-terminal fusion peptide of the measles virus. Remarkably, only MV-197 was highly fusogenic toward large unilamellar vesicles composed of either zwitterionic (phosphatidylcholine or phosphatidylcholine/sphingomyelin/cholesterol, a composition similar to that of human cell membranes) or negatively charged phospholipids. Binding experiments, circular dichroism spectroscopy in phospholipid membranes, and homo energy-transfer studies with fluorescently labeled peptides revealed that MV-197 adopts a predominant alpha-helical structure and shares properties similar to those reported for known fusion peptides. These results suggest that the presence of two fusion peptides in the F1 protein is a general feature of paramyxoviruses.
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Affiliation(s)
- O Samuel
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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20
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Chávez A, Pujol M, Haro I, Alsina MA, Cajal Y. Membrane fusion by an RGD-containing sequence from the core protein VP3 of hepatitis A virus and the RGA-analogue: implications for viral infection. Biopolymers 2001; 58:63-77. [PMID: 11072230 DOI: 10.1002/1097-0282(200101)58:1<63::aid-bip70>3.0.co;2-l] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The interaction of an RGD-containing epitope from the hepatitis A virus VP3 capsid protein and its RGA-analogue with lipid membranes was studied by biophysical methods. Two types of model membrane were used: vesicles and monolayers spread at the air/water interface, with a composition that closely resembles the lipid moiety of hepatocyte membranes: PC/SM/PE/PC (40:33:12:15; PC: 1-palmitoyl-2-oleoylglycero-sn-3-phosphocholine; SM: sphingomyelin from chicken egg yolk; PE, 1,2-dipalmitoyl-phosphatidylethanolamine; PS: L-alpha-phosphatidyl-L-serine from bovine brain). In addition, zwitterionic PC/SM/PE (47:39:14) and cationic PC/SM/PE/DOTAP (40:33:12:15; DOTAP: 1,2-dioleoyl-3-trimethylammonium-propane) membranes were also prepared in order to dissect the electrostatic and hydrophobic components in the interaction. Changes in tryptophan fluorescence, acrylamide quenching, and resonance energy transfer experiments in the presence of vesicles, as well as the kinetics of insertion in monolayers, indicate that both peptides bind to the three types of membrane at neutral and acidic pH; however, binding is irreversible only at low pH. Membrane-destabilizing and fusogenic activities are triggered by acidification at pH 4-6, characteristic of the endosome. Fluorescence experiments show that VP3-RGD and VP3-RGA induce mixing of lipids and leakage or mixing of aqueous contents in anionic and cationic vesicles at pH 4-6, indicating leaky fusion. Interaction with zwitterionic vesicles (PC/SM/PE) results in leakage without lipid mixing, indicating pore formation. Replacement of aspartic acid in the RGD motif by alanine maintains the membrane-destabilizing properties of the peptide at low pH, but not its antigenicity. Since the RGD tripeptide is related to receptor-mediated cell adhesion and antigenicity, results suggest that receptor binding is not a molecular requirement for fusion. The possible involvement of peptide-induced membrane destabilization in the mechanism of hepatitis A virus infection of hepatocytes by the endosomal route is discussed.
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Affiliation(s)
- A Chávez
- Department of Physical Chemistry, School of Pharmacy, University of Barcelona, Avn. Joan XXIII s/n, 08028 Barcelona, Spain
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21
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Abstract
Although membrane fusion occurs ubiquitously and continuously in all eukaroytic cells, little is known about the mechanism that governs lipid bilayer fusion associated with any intracellular fusion reactions. Recent studies of the fusion of enveloped viruses with host cell membranes have helped to define the fusion process. The identification and characterization of key proteins involved in fusion reactions have mainly driven recent advances in our understanding of membrane fusion. The most important denominator among the fusion proteins is the fusion peptide. In this review, work done in the last few years on the molecular mechanism of viral membrane fusion will be highlighted, focusing in particular on the role of the fusion peptide and the modification of the lipid bilayer structure. Much of what is known regarding the molecular mechanism of viral membrane fusion has been gained using liposomes as model systems in which the molecular components of the membrane and the environment are strictly controlled. Many amphilphilic peptides have a high affinity for lipid bilayers, but only a few sequences are able to induce membrane fusion. The presence of alpha-helical structure in at least part of the fusion peptide is strongly correlated with activity whereas, beta-structure tends to be less prevalent, associated with non-native experimental conditions, and more related to vesicle aggregation than fusion. The specific angle of insertion of the peptides into the membrane plane is also found to be an important characteristic for the fusion process. A shallow penetration, extending only to the central aliphatic core region, is likely responsible for the destabilization of the lipids required for coalescence of the apposing membranes and fusion.
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Affiliation(s)
- I Martin
- Laboratoire de Chimie-Physique des Macromolécules aux Interfaces (LPCMI) CP206/2, Université Libre de Bruxelles, Brussels, Belgium.
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22
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Affiliation(s)
- D C Drummond
- Research Institute, California Pacific Medical Center, 94115, San Francisco, CA, USA
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23
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Balliet JW, Gendron K, Bates P. Mutational analysis of the subgroup A avian sarcoma and leukosis virus putative fusion peptide domain. J Virol 2000; 74:3731-9. [PMID: 10729148 PMCID: PMC111882 DOI: 10.1128/jvi.74.8.3731-3739.2000] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Short hydrophobic regions referred to as fusion peptide domains (FPDs) at or near the amino terminus of the membrane-anchoring subunit of viral glycoproteins are believed to insert into the host membrane during the initial stage of enveloped viral entry. Avian sarcoma and leukosis viruses (ASLV) are unusual among retroviruses in that the region in the envelope glycoprotein (EnvA) proposed to be the FPD is internal and contains a centrally located proline residue. To begin analyzing the function of this region of EnvA, 20 substitution mutations were introduced into the putative FPD. The mutant envelope glycoproteins were evaluated for effects on virion incorporation, receptor binding, and infection. Interestingly, most of the single-substitution mutations had little effect on any of these processes. In contrast, a bulky hydrophobic substitution for the central proline reduced viral titers 15-fold without affecting virion incorporation or receptor binding, whereas substitution of glycine for the proline had only a nominal effect on EnvA function. Similar to other viral FPDs, the putative ASLV FPD has been modeled as an amphipathic helix where most of the bulky hydrophobic residues form a patch on one face of the helix. A series of alanine insertion mutations designed to interrupt the hydrophobic patch on the helix had differential effects on infectivity, and the results of that analysis together with the results observed with the substitution mutations suggest no correlation between maintenance of the hydrophobic patch and glycoprotein function.
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Affiliation(s)
- J W Balliet
- Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6076, USA
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24
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Rodríguez-Crespo I, Yélamos B, Albar JP, Peterson DL, Gavilanes F. Selective destabilization of acidic phospholipid bilayers performed by the hepatitis B virus fusion peptide. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1463:419-28. [PMID: 10675518 DOI: 10.1016/s0005-2736(99)00231-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A peptide corresponding to the N-terminal region of the S protein of hepatitis B virus (Met-Glu-Asn-Ile-Thr-Ser-Gly-Phe-Leu-Gly-Pro-Leu-Leu-Val-Leu-Gln) has been previously demonstrated to perform aggregation and destabilization of acidic liposome bilayers and to adopt a highly stable beta-sheet conformation in the presence of phospholipids. The changes in the lipid moiety produced by this peptide have been followed by fluorescence depolarization and electron microscopy. The later was employed to determine the size and shape of the peptide-vesicle complexes, showing the presence of highly aggregated and fused structures only when negatively charged liposomes were employed. 1,6-Diphenyl-1,3,5-hexatriene depolarization measurements showed that the interaction of the peptide with both negatively charged and zwitterionic liposomes was accompanied by a substantial reduction of the transition amplitude without affecting the temperature of the gel-to-liquid crystalline phase transition. These data are indicative of the peptide insertion inside the bilayer of both types of liposomes affecting the acyl chain order, though only the interaction with acidic phospholipids leads to aggregation and fusion. This preferential destabilization of the peptide towards negatively charged phospholipids can be ascribed to the electrostatic interactions between the peptide and the polar head groups, as monitored by 1-(4-(trimethylammoniumphenyl)-6-phenyl-1,3, 5-hexatriene fluorescence depolarization analysis.
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Affiliation(s)
- I Rodríguez-Crespo
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, 28040, Madrid, Spain
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25
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Abstract
Cell life depends on the dynamics of molecular processes: molecule folding, organelle building and transformations involving membrane fusion, protein activation and degradation. To carry out these processes, the hydrophilic/hydrophobic interfaces of amphipathic systems such as membranes and native proteins must be disrupted. In the past decade, protein fragments acting in the disruption of interfaces have been evidenced: they are named the tilted or oblique peptides. Due to a peculiar distribution of hydrophobicity, they can disrupt hydrophobicity interfaces. Tilted peptides should be present in many proteins involved in various stages of cell life. This hypothesis overviews their discovery, describes how they are detected and discusses how they could be involved in dynamic biological processes.
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Affiliation(s)
- R Brasseur
- Centre de Biophysique Moléculaire Numérique, Faculté Universitaire des Sciences Agronomiques de Gembloux, Belgium.
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26
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Martin I, Ruysschaert J, Epand RM. Role of the N-terminal peptides of viral envelope proteins in membrane fusion. Adv Drug Deliv Rev 1999; 38:233-255. [PMID: 10837759 DOI: 10.1016/s0169-409x(99)00031-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Membrane fusion is an important biological process that is observed in a wide variety of intra and intercellular events. In this review, work done in the last few years on the molecular mechanism of viral membrane fusion is highlighted, focusing in particular on the role of the fusion peptide and the modification of the lipid bilayer structure. While the Influenza hemagglutinin is currently the best understand fusion protein, there is still much to be learned about the key events in enveloped virus fusion reactions. This review compares our current understanding of the membrane fusion activity of Influenza and retrovirus viruses. We shall be concerned especially with the studies that lead to interpretations at the molecular level, so we shall concentrate on model membrane systems where the molecular components of the membrane and the environment are strictly controlled.
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Affiliation(s)
- I Martin
- Laboratoire de Chimie-Physique des Macromolécules aux Interfaces (LCPMI) CP206/2, Université Libre de Bruxelles. 1050, Brussels, Belgium
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27
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Rodríguez-Crespo I, Núñez E, Yélamos B, Gómez-Gutiérrez J, Albar JP, Peterson DL, Gavilanes F. Fusogenic activity of hepadnavirus peptides corresponding to sequences downstream of the putative cleavage site. Virology 1999; 261:133-42. [PMID: 10441561 DOI: 10.1006/viro.1999.9823] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sequence homology between the amino-terminal region of the S protein of hepatitis B Virus (HBV) and known fusion peptides from retroviruses and paramyxoviruses led us to propose that this region might be equally involved in the initial infective steps of hepadnaviruses. In fact, we showed that a synthetic peptide corresponding to the N-terminus region of the S protein of HBV had membrane-interacting properties and was able to induce liposome fusion adopting an extended (beta-sheet) conformation (Rodríguez-Crespo et al., 1996, 1995). We describe herein studies on the interaction of peptides derived from the N-terminal region of the S protein of duck (DHBV: Met-Ser-Gly-Thr-Phe-Gly-Gly-Ile-Leu-Ala-Gly-Leu-Ile-Gly-Leu-Leu) and woodchuck hepatitis B viruses (WHV: Met-Ser-Pro-Ser-Ser-Leu-Leu-Gly-Leu-Leu-Ala-Gly-Leu-Gln-Val-Val) with liposomes. These peptides were able to induce to a different extent aggregation, lipid mixing, and leakage of internal aqueous contents from both neutral and negatively charged phospholipid vesicles in a concentration-dependent and pH-independent manner. Fluorescence depolarization of 1,6-diphenyl-1,3,5-hexatriene-labeled vesicles indicated that both peptides become inserted into the hydrophobic core of the lipid bilayer. Circular dichroism studies indicated that the DHBV peptide adopts an extended conformation in the presence of lipids, whereas the WHV peptide displays a high content of alpha-helical conformation. Therefore, these results extend our previous findings obtained for human hepatitis B virus to other members of the hepadnavirus family and suggest that this region of the S protein is important in the initial steps of the infective cycle.
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Affiliation(s)
- I Rodríguez-Crespo
- Facultad de Ciencias Químicas, Universidad Complutense, Madrid, 28040, Spain
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28
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Epand RF, Macosko JC, Russell CJ, Shin YK, Epand RM. The ectodomain of HA2 of influenza virus promotes rapid pH dependent membrane fusion. J Mol Biol 1999; 286:489-503. [PMID: 9973566 DOI: 10.1006/jmbi.1998.2500] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To better understand the roles of different regions of influenza hemagglutinin in membrane fusion, we have studied the fusion properties of large unilamellar vesicles in the presence of constructs comprising the 127 amino acid ectodomain of the HA2 fragment (FHA2) as well as mutated forms of FHA2 containing single amino acid substitutions, the 95 amino acid truncated form of FHA2 lacking the N-terminal fusion peptide (SHA2), the 20 amino acid N-terminal fusion peptide and the ten amino acid peptide corresponding to the kinked loop region of FHA2. The 100 nm liposomes were made from dioleoylphosphatidylethanolamine, dioleoylphosphatidylcholine and cholesterol in equimolar ratio. At pH 5 a high rate of lipid mixing was observed with FHA2 present, even at very low molar concentrations, whereas much lower rates were observed using the shorter constructs: SHA2, the fusion peptide, and the loop peptide. Concentrations of FHA2 which promoted extensive lipid mixing also induced leakage of aqueous contents. Marked effects of FHA2 were also observed with liposomes of egg phosphatidylcholine. All of the changes observed with the liposomes were highly pH-dependent, with only negligible changes occurring at pH 7. The results demonstrate the potent action of FHA2 in promoting lipid mixing and demonstrate the contribution of other regions of the ectodomain of FHA2, in addition to the fusion peptide, to the mechanism of acceleration of membrane fusion. The results also indicate that the pH dependence of fusion is not due solely to changes in the interactions between the HA1 and HA2 subunits. Thus, the "spring loaded energy" is not required to bring about the apposition of the two membranes, considering that FHA2 is already in its thermostable conformation. The acidic amino acid residues in the kinked loop region appear to play a particularly important role in the pH-dependent fusion process as demonstrated by the marked loss of lipid mixing activity of mutant forms of FHA2.
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Affiliation(s)
- R F Epand
- McMaster University Health Sciences Centre, 1200 Main Street West, Hamilton, ON, L8N 3Z5, Canada.
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29
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Nir S, Nicol F, Szoka FC. Surface aggregation and membrane penetration by peptides: relation to pore formation and fusion. Mol Membr Biol 1999; 16:95-101. [PMID: 10332743 DOI: 10.1080/096876899294814] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The peptide GALA undergoes a conformational change to an amphipathic alpha-helix when the pH is reduced, inducing leakage of contents from vesicles. Leakage from neutral or negatively-charged vesicles at pH 5.0 was similar and could be adequately explained by a mathematical model which assumed that GALA becomes incorporated into the vesicle bilayer and irreversibly aggregates to form a pore consisting of M = 10 +/- 2 peptides. Increasing cholesterol content in the membranes resulted in reduced leakage, and increased reversibility of surface aggregation of the peptide. Employing fluorescently labelled peptides confirmed that the degree of reversibility of surface aggregation of GALA was significantly larger in cholesterol containing liposomes. Orientation of the peptide GALA in bilayers was determined by a bodipy-avidin/biotin binding assay. The peptide was labelled by biotin at the N- or C-terminus and bodipy-avidin molecules were added externally or were preencapsulated in the vesicles. The peptides are arranged in the pore perpendicularly to the membrane, such that 3/4 of the N-termini are on the internal side of the membrane. The pores are stable and persist for at least 10 min. When the peptides form an aggregate of size smaller than M, the orientation of the peptide is mostly parallel to the surface and the biotinylated peptide does not translocate. When a critical size of the aggregate is attained, a rearrangement of the peptide occurs, which amounts to rapid penetration and formation of a pore structure. Induction of fusion by peptides may be antagonistic to pore formation, the outcome being dependent on vesicle aggregation.
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Affiliation(s)
- S Nir
- Seagram Center for Soil and Water Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot, Israel.
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30
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Cortese JD, Voglino LA, Hackenbrock CR. Novel fluorescence membrane fusion assays reveal GTP-dependent fusogenic properties of outer mitochondrial membrane-derived proteins. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1371:185-98. [PMID: 9630622 DOI: 10.1016/s0005-2736(97)00266-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have shown that fusion of small unilamellar vesicles (SUV) with outer mitochondrial membranes occurs at physiological pH [Cortese et al., 1991, J. Cell Biol., Vol. 113, 1331-1340]. The proteins driving this process could be involved in mitochondrial membrane fusion, which is presently poorly understood. In this study, we release from rat liver mitochondria a soluble protein fraction (SF) that increases fusion at neutral pH measured by membrane fusion assays (MFAs). Since this fusogenic activity was specifically enhanced by GTP, we separate SF by GTP affinity chromatography into: i) a flow-through subfraction (G1) containing numerous proteins with low GTP affinity; and ii) a subfraction (G2) which may contain GTP-binding proteins. A novel array of MFAs is developed to study the fusogenic properties of these fractions, measuring the merging of membranes (membrane-mixing) or the mixing of intravesicular aqueous contents (content-mixing). The MFAs use: a) SUV/large unilamellar vesicles, lacking mitochondrial membranes; b) SUV/mitochondria, reconstituting membrane-mitochondrial interactions; and c) mitochondria/mitochondria, mimicking mitochondrial fusion. The results indicate that: i) G1 contains GTP-independent, in vitro fusogenic proteins that are not sufficient to induce mitochondrial fusion; and ii) G2 contains GTP-dependent proteins that stimulate mitochondrial fusion at neutral pH. The MFAs described here could be used to monitor the isolation of active proteins from these subfractions and to define the mechanism of intermitochondrial membrane fusion.
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Affiliation(s)
- J D Cortese
- Department of Cell Biology and Anatomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7090, USA.
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31
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Nuñez E, Fernandez AM, Estepa A, Gonzalez-Ros JM, Gavilanes F, Coll JM. Phospholipid interactions of a peptide from the fusion-related domain of the glycoprotein of VHSV, a fish rhabdovirus. Virology 1998; 243:322-30. [PMID: 9580549 DOI: 10.1006/viro.1998.9076] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies mapped a p2 domain (aa 82-109) which binds phosphatidylserine (PS) (Estepa and Coll, 1996a) and contains three contiguous hydrophobic amino acid heptad repeats followed by a positively charged stretch (Coll, 1995b) in the glycoprotein G of the viral hemorrhagic septicemia virus (VHSV), a fish rhabdovirus. Anti-p2 antibodies inhibited low-pH VHSV-induced fusion (Estepa and Coll, 1997) and low-pH PS binding to VHSV (Estepa and Coll, 1996a). We report here further studies on the interaction of the synthetic peptide p2 with phospholipid vesicles. The synthetic p2 peptide was able to mediate aggregation, lipid mixing, and leakage of contents only with negatively charged phospholipid vesicles and in a concentration-dependent manner. As shown by its effect on lipid phase transitions deduced from data with fluorescence polarization and differential scanning calorimetry, the p2 peptide becomes inserted into the hydrophobic negatively charged phospholipid vesicle bilayers. In addition, data based on circular dichroism showed that the p2 peptide folds as a structure with a high content of beta-sheets stabilized by interaction with anionic phospholipids. These studies are potentially relevant to viral fusion in VHSV.
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Affiliation(s)
- E Nuñez
- Departamento de Bioquímica y Biología Molecular, Ciencias Químicas, Universidad Complutense, Madrid, Spain
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32
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Davies SM, Kelly SM, Price NC, Bradshaw JP. Structural plasticity of the feline leukaemia virus fusion peptide: a circular dichroism study. FEBS Lett 1998; 425:415-8. [PMID: 9563505 DOI: 10.1016/s0014-5793(98)00274-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The secondary structure of the feline leukaemia virus (FeLV) fusion peptide was investigated using circular dichroism (CD). Our results show that this peptide can readily flip between random, alpha-helical and beta-sheet conformations, depending upon its environment. The CD spectrum changes from one characteristic of random coil to predominantly beta-sheet type, and finally to that showing the characteristics of alpha-helical structure on moving from an aqueous solvent, through several increasingly hydrophobic systems, to a highly hydrophobic solvent. Electron microscopy confirmed the presence of beta structure. We propose that the structural plasticity demonstrated here is crucial to the ability of the fusion peptide to perturb lipid bilayers, and thus promote membrane fusion.
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Affiliation(s)
- S M Davies
- Department of Preclinical Veterinary Sciences, Royal (Dick) School of Veterinary Studies, University of Edinburgh, UK.
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33
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Pecheur EI, Martin I, Ruysschaert JM, Bienvenue A, Hoekstra D. Membrane fusion induced by 11-mer anionic and cationic peptides: a structure-function study. Biochemistry 1998; 37:2361-71. [PMID: 9485383 DOI: 10.1021/bi972697f] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We recently demonstrated that an amphipathic net-negatively charged peptide consisting of 11 amino acids (WAE 11) strongly promotes fusion of large unilamellar liposomes (LUV) when anchored to a liposomal membrane [Pecheur, E. I., Hoekstra, D., Sainte-Marie, J., Maurin, L., Bienvenue, A., and Philippot, J. R. (1997) Biochemistry 36, 3773-3781]. To elucidate a potential relationship between peptide structure and its fusogenic properties and to test the hypothesis that specific structural motifs are a prerequisite for WAE-induced fusion, three 11-mer WAE-peptide analogues (WAK, WAEPro, and WAS) were synthesized and investigated for their structure and fusion activity. Structural analysis of the synthetic peptides by infrared attenuated total reflection spectroscopy reveals a distinct propensity of each peptide toward a helical structure after their anchorage to a liposomal surface, emphasizing the importance of anchorage on conveying a secondary structure, thereby conferring fusogenicity to these peptides. However, whereas WAE and WAK peptides displayed an essentially nonleaky fusion process, WAS- and WAEPro-induced fusion was accompanied by substantial leakage. It appears that peptide helicity as such is not a sufficient condition to convey optimal fusion properties to these 11-mer peptides. Studies of changes in the intrinsic Trp fluorescence and iodide quenching experiments were carried out and revealed the absence of migration of the Trp residue of WAS and WAEPro to a hydrophobic environment, upon their interaction with the target membranes. These results do not support the penetration of both peptides as their mode of membrane interaction and destabilization but rather suggest their folding along the vesicle surface, posing them as surface-seeking helixes. This is in striking contrast to the behavior observed for WAE and WAK, for which at least partial penetration of the Trp residue was demonstrated. These results indicate that subtle differences in the primary sequence of a fusogenic peptide could induce dramatic changes in the way the peptide interacts with a bilayer, culminating in equally drastic changes in their functional properties. The data also reveal a certain degree of sequence specificity in WAE-induced fusion.
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Affiliation(s)
- E I Pecheur
- Department of Physiological Chemistry, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
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34
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Lelièvre D, Hsu SC, Daubos P, Favard C, Vigny P, Trudelle Y, Steward MW, Delmas A. Structural properties of chimeric peptides containing a T-cell epitope linked to a fusion peptide and their importance for in vivo induction of cytotoxic T-cell responses. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 249:895-904. [PMID: 9395341 DOI: 10.1111/j.1432-1033.1997.00895.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have previously shown that when administered to mice without adjuvant, a chimeric peptide consisting of the fusion peptide F from measles virus protein linked at the C-terminus of a cytotoxic T-cell epitope from the M2 protein of respiratory syncytial virus efficiently primes for an major histocompatibility complex (MHC) class-I restricted cytotoxic T lymphocyte (CTL) response. In this report, we demonstrated by microspectrofluorometry that the fusion-peptide moiety bound to the plasma membrane of living cells. When the fusion peptide was linked to the C-terminus of the CTL epitope, the chimeric peptide (M2-F) adopted a marked beta-sheet conformation. In contrast, when the fusion peptide was linked to the N-terminus of the T-cell epitope (F-M2), the chimeric peptide adopted an alpha-helical conformation in the presence of trifluoroethanol. The immunogenicity of the two chimeric peptides for class-I restricted CTL was also significantly different, the one adopting the alpha-helical conformation being more immunogenic. Probably due to its obvious conversion to an alpha-helical conformation, the F-M2 peptide could have a higher propensity to insert into membranes, as shown by microspectrofluorometry, with a resultant better immunogenicity than the M2-F peptide.
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Affiliation(s)
- D Lelièvre
- Centre de Biophysique Moléculaire, UPR 4301 CNRS, Orléans, France
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35
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Longo ML, Waring AJ, Hammer DA. Interaction of the influenza hemagglutinin fusion peptide with lipid bilayers: area expansion and permeation. Biophys J 1997; 73:1430-9. [PMID: 9284310 PMCID: PMC1181042 DOI: 10.1016/s0006-3495(97)78175-x] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Fusion is a crucial event in the infection of animal cells by enveloped viruses (e.g., HIV or influenza). Viral fusion is mediated by glycoproteins, spanning the viral envelope, which attach to a membrane surface and induce fusion of the viral envelope to the cellular membrane. Influenza fusion protein (hemagglutinin) contains an amino-terminal segment critical to fusion, referred to as the fusion peptide. We show here that the native fusion peptide (wt-20) of hemagglutinin destabilizes membranes formed of 99% 1 -stearoyl-2-oleoylphosphatidylcholine (SOPC). The first step in destabilization is rapid insertion of the peptide into the membrane, in which membrane area increases by as much as 11% in just seconds. We visualized and quantified the area expansion by using optical video microscopy combined with micropipette aspiration. This rapid membrane area expansion is followed by the formation of membrane defects in the size range of 0.5 nm, and results in membrane rupture. Both the rate of area increase and maximum area increase are significantly higher at a pH near 5.0 compared to pH 7.0. These results suggest that enhanced membrane insertion of wt-20 and accompanying area expansion at pH 5.0 are responsible for the relatively greater lytic activity at this pH. We show that a deletion of the N-terminal glycine of wt-20 results in a lack of area expansion or membrane perturbation at pH 5.0.
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Affiliation(s)
- M L Longo
- School of Chemical Engineering, Cornell University, Ithaca, New York 14853, USA
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36
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Colotto A, Epand RM. Structural study of the relationship between the rate of membrane fusion and the ability of the fusion peptide of influenza virus to perturb bilayers. Biochemistry 1997; 36:7644-51. [PMID: 9201905 DOI: 10.1021/bi970382u] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The amino-terminal segment of the HA2 protein of influenza virus (fusion peptide) has been identified as an important region for membrane fusion. The wild type virus can fuse to membranes more rapidly at pH 5 than at pH 7.4. It has been demonstrated that there is a relationship between the ability of the peptide to promote the formation of inverted phases and the fusogenicity of the intact virus. In this work, we use small-angle X-ray diffraction to study the mechanism of the structural effect of the peptide, at different pHs, on lipid systems characterized by each having a different spontaneous radius of curvature. The overall results show that the action of the peptide on the polymorphism of the lipid systems investigated is strongly pH-dependent. In particular, a rapid formation of cubic phases at pH 5.0 is observed in the presence of this fusion peptide. The ability of the fusion peptide to promote cubic phases exhibits the same dependence on the pH as does the fusogenicity of the intact virus. It is proposed that the peptide promotes cubic phases at pH 5.0 by changing the kinetics of the lamellar to inverted phase transitions.
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Affiliation(s)
- A Colotto
- Department of Biochemistry, McMaster University, Health Sciences Centre, Hamilton, Ontario, Canada
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37
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Pécheur EI, Hoekstra D, Sainte-Marie J, Maurin L, Bienvenüe A, Philippot JR. Membrane anchorage brings about fusogenic properties in a short synthetic peptide. Biochemistry 1997; 36:3773-81. [PMID: 9092806 DOI: 10.1021/bi9622128] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The fusogenic properties of an amphipathic net-negative peptide (wae 11), consisting of 11 amino acid residues, were studied. We demonstrate that, whereas the free peptide displays no significant fusion activity, membrane fusion is strongly promoted when the peptide is anchored to a liposomal membrane. The fusion activity of the peptide appears to be independent of pH, and membrane merging is an essentially nonleaky process. Thus, the extents of lipid mixing and contents mixing were virtually indistinguishable. Vesicle aggregation is a prerequisite for fusion. For this process to take place, the target membranes required a positive charge which was provided by incorporating lysine-coupled phosphatidylethanolamine (PElys). The coupled peptide, present in one population, could thus cause vesicle aggregation via nonspecific electrostatic interaction with PElys. However, the free peptide failed to induce aggregation of PElys vesicles, suggesting that the spatial orientation of the coupled peptide codetermined its ability to bring about vesicle aggregation and fusion. With the monitoring of changes in the intrinsic Trp fluorescence, in conjunction with KI-quenching studies, it would appear that hydrophobic interactions facilitate the fusion event, possibly involving (partial) peptide penetration. Such a penetration may be needed to trigger formation of a transient, nonbilayer structure. Since lysophosphatidylcholine inhibited while monoolein strongly stimulated peptide-induced fusion, our data indicate that wae 11-induced fusion proceeds according to a model consistent with the stalk-pore hypothesis for membrane fusion.
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Affiliation(s)
- E I Pécheur
- UMR 5539 CNRS, Dynamique Moléculaire des Interactions Membranaires, Dépt Biologie Santé, Université Montpellier II, France.
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38
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Bailey AL, Monck MA, Cullis PR. pH-induced destabilization of lipid bilayers by a lipopeptide derived from influenza hemagglutinin. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1324:232-44. [PMID: 9092710 DOI: 10.1016/s0005-2736(96)00228-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A synthetic twenty-one amino acid peptide (AcE4K) based on the amino acid sequence of the influenza HA2 fusion peptide was coupled to a distearoylglycerol lipid anchor by amidation of an N-terminal lysine side chain. The secondary structure of Lipo-AcE4K incorporated into POPC (1-palmitoyl-2-oleoyl-sn-phosphatidylcholine) liposomes was not measurably affected by pH, but increased membrane penetration was indicated by tryptophan fluorescence. At outer monolayer concentrations up to 10 mol%, Lipo-AcE4K formed stable liposomes with POPC and EPC/Chol (egg phosphatidylcholine/cholesterol) (55:45) at pH 7.5. Acid-induced destabilization and fusion of these vesicles were demonstrated by fluorescent lipid mixing and contents leakage assays, and by freeze-fracture electron microscopy. Membrane destabilization increased with increasing lipopeptide concentrations, decreasing pH, inclusion of cholesterol, and incorporation of lipopeptide into the inner monolayer as well as the outer monolayer of the liposomes. Fusion of liposomes bearing Lipo-AcE4K with erythrocyte ghosts was demonstrated by lipid mixing and fluorescence microscopy.
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Affiliation(s)
- A L Bailey
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada.
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39
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Soltesz SA, Hammer DA. Lysis of Large Unilamellar Vesicles Induced by Analogs of the Fusion Peptide of Influenza Virus Hemagglutinin. J Colloid Interface Sci 1997; 186:399-409. [PMID: 9056369 DOI: 10.1006/jcis.1996.4670] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We have developed a micropipette aspiration assay to observe the lysis of large (20-30 &mgr;m diameter) vesicles aspirated using micropipettes. Single membrane lysis events can be seen with the light microscope and are followed using fluorescence assays and video microscopy. In this study, we have examined the ability of two analogs of the fusion peptide from influenza virus hemagglutinin to induce the lysis of large unilamellar egg phosphatidylcholine vesicles, as a function of peptide concentration and pH. X31 is a wild-type peptide from one strain of Influenza A, and E5 is an analogue which has several residues replaced by glutamate residues. Both peptides were found to induce lysis of large vesicles in a pH-dependent manner. Both peptides exhibited maximal activity at pH 5, measured in terms of both rate and extent of lysis. E5 was active at much lower concentrations than X31. Our results with both peptides are compared to results published from other laboratories.
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Affiliation(s)
- SA Soltesz
- School of Chemical Engineering, Cornell University, Ithaca, New York, 14853
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40
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Nicol F, Nir S, Szoka FC. Effect of cholesterol and charge on pore formation in bilayer vesicles by a pH-sensitive peptide. Biophys J 1996; 71:3288-301. [PMID: 8968598 PMCID: PMC1233816 DOI: 10.1016/s0006-3495(96)79521-8] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The effect of cholesterol on the bilayer partitioning of the peptide GALA (WEAALAEALAEALAEHLAEALAEALEALAA) and its assembly into a pore in large unilamellar vesicles composed of neutral and negatively charged phospholipids has been determined. GALA undergoes a conformational change from a random coil to an amphipathic alpha-helix when the pH is reduced from 7.0 to 5.0, inducing at low pH leakage of contents from vesicles. Leakage from neutral or negatively charged vesicles at pH 5.0 was similar and could be adequately explained by the mathematical model (Parente, R. A., S. Nir, and F. C. Szoka, Jr., 1990. Mechanism of leakage of phospholipid vesicle contents induced by the peptide GALA. Biochemistry. 29:8720-8728) which assumed that GALA becomes incorporated into the vesicle bilayer and irreversibly aggregates to form a pore consisting of 10 +/- 2 peptides. Increasing cholesterol content in the membranes resulted in a reduced efficiency of the peptide to induce leakage. Part of the cholesterol effect was due to reduced binding of the peptide to cholesterol-containing membranes. An additional effect of cholesterol was to increase reversibility of surface aggregation of the peptide in the membrane. Results could be explained and predicted with a model that retains the same pore size, i.e., 10 +/- 2 peptides, but includes reversible aggregation of the monomers to form the pore. Resonance energy transfer experiments using fluorescently labeled peptides confirmed that the degree of reversibility of surface aggregation of GALA was significantly larger in cholesterol-containing liposomes, thus reducing the efficiency of pore formation.
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Affiliation(s)
- F Nicol
- University of California, School of Pharmacy, Department of Biopharmaceutics, San Francisco 94143-0446, USA
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41
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Tian P, Ball JM, Zeng CQ, Estes MK. The rotavirus nonstructural glycoprotein NSP4 possesses membrane destabilization activity. J Virol 1996; 70:6973-81. [PMID: 8794341 PMCID: PMC190747 DOI: 10.1128/jvi.70.10.6973-6981.1996] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
During a unique morphogenetic process, rotaviruses obtain a transient membrane envelope when newly synthesized subviral particles bud into the endoplasmic reticulum (ER). As rotavirus particles mature, they lose their transient membrane and a layer of the glycoprotein VP7 forms the virion outer capsid shell. The nonstructural glycoprotein NSP4 functions as an intracellular receptor in the ER membrane (K. S. Au, W. K. Chan, J. W. Burns, and M. K. Estes, J. Virol. 63:4553-4562, 1989), and it has been hypothesized that NSP4 is involved in the removal of the envelope during viral morphogenesis (M. K. Estes and J. Cohen, Microbiol. Rev. 53:410-449, 1989; B. L. Petrie, M. K. Estes, and D. Y. Graham, J. Virol. 46:270-274, 1983). The purpose of the present study was to determine if NSP4 has a direct membrane destabilization activity (MDA) by using liposome leakage assays and electron microscopic visualization of liposome, microsome, and viral envelope disruption. The fluorescent marker (calcein) incorporated into liposomes was released when the liposomes were incubated with purified NSP4. A region corresponding to amino acid residues 114 to 135 of NSP4 also released calcein from liposomes. NSP4(114-135) peptide-specific antibody completely blocked the MDA of the purified NSP4 protein. These results suggest that this region contains at least part of the functional domain of NSP4. Liposomes composed of phosphatidylcholine and microsomes (to simulate ER membranes) were broken when observed by electron microscopy after incubation with NSP4 or the NSP4(114-135) peptide. In contrast, the envelope of Sendai virus, which is derived from cytoplasmic membranes, and erythrocytes were not disrupted by NSP4 and the NSP4(114-135) peptide. These results provide direct evidence that NSP4 possesses MDA and suggest that it can cause ER membrane damage. Therefore, NSP4 might play an important role in the removal of the transient envelope from budding particles during viral morphogenesis. A model for the MDA of NSP4 in viral morphogenesis is proposed.
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Affiliation(s)
- P Tian
- Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030, USA
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42
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Abstract
The mechanism of leakage induced by surface active peptides is not yet fully understood. To gain insight into the molecular events underlying this process, the leakage induced by the peptide pardaxin from phosphatidylcholine/ phosphatidylserine/cholesterol large unilamellar vesicles was studied by monitoring the rate and extent of dye release and by theoretical modeling. The leakage occurred by an all-or-none mechanism: vesicles either leaked or retained all of their contents. We further developed a mathematical model that includes the assumption that certain peptides become incorporated into the vesicle bilayer and aggregate to form a pore. The current experimental results can be explained by the model only if the surface aggregation of the peptide is reversible. Considering this reversibility, the model can explain the final extents of calcein leakage for lipid/peptide ratios of > 2000:1 to 25:1 by assuming that only a fraction of the bound peptide forms pores consisting of M = 6 +/- 3 peptides. Interestingly, less leakage occurred at 43 degrees C, than at 30 degrees C, although peptide partitioning into the bilayer was enhanced upon elevation of the temperature. We deduced that the increased leakage at 30 degrees C was due to an increase in the extent of reversible surface aggregation at the lower temperature. Experiments employing fluorescein-labeled pardaxin demonstrated reversible aggregation of the peptide in suspension and within the membrane, and exchange of the peptide between liposomes. In summary, our experimental and theoretical results support reversible surface aggregation as the mechanism of pore formation by pardaxin.
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Affiliation(s)
- D Rapaport
- Department of Membrane Research and Biophysics, Weizmann Institute of Science, Hebrew University of Jerusalem, Israel
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43
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Prchla E, Plank C, Wagner E, Blaas D, Fuchs R. Virus-mediated release of endosomal content in vitro: different behavior of adenovirus and rhinovirus serotype 2. J Cell Biol 1995; 131:111-23. [PMID: 7559769 PMCID: PMC2120603 DOI: 10.1083/jcb.131.1.111] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Endosomal penetration by nonenveloped viruses might be accomplished by either local breakdown of the endosomal membrane (e.g., adenovirus) or formation of a membrane-spanning pore by capsid proteins. Uncoating of the nonenveloped virus human rhinovirus serotype 2 (HRV2) has been shown to occur from late endosomes and to be entirely dependent on the acidic pH in this compartment (Prchla, E., E. Kuechler, D. Blaas, and R. Fuchs. 1994. J. Virol. 68: 3713-3723). To investigate further the mechanism of uncoating of HRV2, an in vitro assay was established to test viruses or virus-derived peptides for their capacity to release cointernalized biotin-dextran of different molecular mass (10 and 70 kD) from isolated endosomes. The suitability of the assay was demonstrated by use of a fusogenic peptide derived from influenza virus hemagglutinin (GALA-INF3). Whereas adenovirus induced a low pH-dependent release of up to 46% of the internalized biotin-dextran and did not show any significant size selectivity (as expected for endosome disruption), HRV2 mediated release of 27% of the 10 kD dextran and only traces of the 70-kD dextran. Similarly, GALA-INF3-induced release of biotin-dextran was also size dependent. The potential role of the capsid protein VP1 in HRV2 uncoating in vivo was also substantiated in our in vitro system using an amphipathic, NH2-terminal peptide of VP1. Taken together, these data favor the model of a specific pore-forming mechanism for HRV2 uncoating which is in contrast to the membrane-disrupting mechanism of adenovirus.
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Affiliation(s)
- E Prchla
- Department of General and Experimental Pathology, University of Vienna, Austria
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44
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Soltesz SA, Hammer DA. Micropipette manipulation technique for the monitoring of pH-dependent membrane lysis as induced by the fusion peptide of influenza virus. Biophys J 1995; 68:315-25. [PMID: 7711257 PMCID: PMC1281690 DOI: 10.1016/s0006-3495(95)80190-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We have assembled a micropipette aspiration assay to measure membrane destabilization events in which large (20-30 microns diameter) unilamellar vesicles are manipulated and exposed to membrane destabilizing agents. Single events can be seen with a light microscope and are recorded using both a video camera and a photomultiplier tube. We have performed experiments with a wild-type fusion peptide from influenza virus (X31) and found that it induces pH-dependent, stochastic lysis of large unilamellar vesicles. The rate and extent of lysis are both maximum at pH 5; the maximum rate of lysis is 0.018 s-1 at pH 5. An analysis of our data indicates that the lysis is not correlated either to the size of the vesicles or to the tension created in the vesicle membranes by aspiration.
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Affiliation(s)
- S A Soltesz
- School of Chemical Engineering, Cornell University, Ithaca, New York 14853
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45
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Arnold K. Cation-Induced Vesicle Fusion Modulated by Polymers and Proteins. HANDBOOK OF BIOLOGICAL PHYSICS 1995. [DOI: 10.1016/s1383-8121(06)80012-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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46
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Bongartz JP, Aubertin AM, Milhaud PG, Lebleu B. Improved biological activity of antisense oligonucleotides conjugated to a fusogenic peptide. Nucleic Acids Res 1994; 22:4681-8. [PMID: 7984418 PMCID: PMC308518 DOI: 10.1093/nar/22.22.4681] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Recently several groups reported a dramatic improvement of reporter gene transfection efficiency using a fusogenic peptide, derived from the Influenza hemagglutinin envelop protein. This peptide changes conformation at acidic pH and destabilizes the endosomal membranes thus resulting in an increased cytoplasmic gene delivery. We describe the use of a similar fusogenic peptide in order to improve the antiviral potency of antisense oligodeoxynucleotides (anti TAT) and oligophosphorothioates (S-dC28) on de novo HIV infected CEM-SS lymphocytes in serum-free medium. We observed as 5 to 10 fold improvement of the anti HIV activities of the phosphodiester antisense oligonucleotides after chemical coupling to the peptide in a one to one ratio by a disulfide or thioether bond. No toxicities were observed at the effective doses (0.1-1 microM). No sequence specificity was obtained and the fusogenic peptide possessed some antiviral activities on its own (IC50: 6 microM). A S-dC28-peptide disulfide linked conjugate and a streptavidin-peptide-biotinylated S-dC28 adduct showed similar activities as the free S-dC28 oligonucleotide (IC50: 0.1-1 nM). As expected, all the compounds were less potent in the presence of serum but the relative contribution of peptide coupling was maintained.
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Affiliation(s)
- J P Bongartz
- Institut de Génétique Moléculaire de Montpellier-UMR CNRS 9942, Montpellier, France
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47
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Interaction of fluorescently labeled analogues of the amino-terminal fusion peptide of Sendai virus with phospholipid membranes. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36582-1] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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48
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Muga A, Neugebauer W, Hirama T, Surewicz WK. Membrane interaction and conformational properties of the putative fusion peptide of PH-30, a protein active in sperm-egg fusion. Biochemistry 1994; 33:4444-8. [PMID: 8161498 DOI: 10.1021/bi00181a002] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A peptide representing the putative fusion domain of PH-30, a sperm surface protein involved in sperm-egg fusion, was synthesized, and its interaction with model lipid membranes was characterized by biophysical methods. While the peptide binds to the vesicles composed of both neutral and acidic lipids, the apparent affinity is significantly higher for the latter lipid class. The intervesicular lipid mixing assay suggests that the synthetic peptide is able to induce fusion of large unilamellar vesicles. Circular dichroism and Fourier-transform infrared spectroscopy show that while in an aqueous buffer the peptide exists in an essentially unordered conformation, binding to the membranes results in a conformational transition to a beta-structure. These data indicate that the fragment identified on the alpha-subunit of PH-30 as a putative fusion peptide is indeed a good candidate for this role. However, in contrast to what has been proposed for some viral fusion peptides, the PH-30 fusion domain is highly unlikely to act as an insertional "sided" helix.
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Affiliation(s)
- A Muga
- Institute for Biological Sciences, National Research Council of Canada, Ottawa
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49
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50
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Ishiguro R, Kimura N, Takahashi S. Orientation of fusion-active synthetic peptides in phospholipid bilayers: determination by Fourier transform infrared spectroscopy. Biochemistry 1993; 32:9792-7. [PMID: 8373779 DOI: 10.1021/bi00088a034] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A group of synthetic peptides having an amino acid sequence related to the N-terminal region of the influenza virus hemagglutinin HA-2 chain can induce phospholipid membrane fusion in a pH-dependent manner. These peptides bind to membranes to form alpha-helices even at pH's where no fusion activity is seen. We determined the orientation of these alpha-helical peptides in lipid multibilayers using attenuated total reflection infrared spectroscopy and found that the peptide alpha-helices took a preferential orientation, the helix axis being about 70 degrees from the normal of the membrane plane, or in other words rather parallel to the membrane plane. The orientation was almost independent of pH and a modification of the N-terminal amino group which reduced the fusion activity of the peptides. The determination was carried out for peptides in lipid multibilayers in dry or hydrated (membranes equilibrated with D2O vapor) conditions. Although a slight decrease in the helix orientation angle from the membrane normal was noticed for a hydrated system, the difference between the results for dry and hydrated conditions was small.
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Affiliation(s)
- R Ishiguro
- Institute for Chemical Research, Kyoto University, Japan
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