Lysophosphatidylcholine mediates the mode of insertion of the NH<sub>2</sub>‐terminal SIV fusion peptide into the lipid bilayer

Martin, Isabelle; Dubois, M C; Særmark, T.; Epand, Richard M.; Ruysschaert, Jean Marie

doi:10.1016/0014-5793(93)80680-s

Cited by 30 publications

(25 citation statements)

References 34 publications

(18 reference statements)

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“…Specifically, it has been shown that the presence of lipids with an inverted-cone shape (which induce positive curvature) such as lysophosphatidylcholine (LPC) in the outer leaflet of target membranes impaired fusion, whereas fusion was promoted at least in some instances by cone-shaped lipids (which induce negative curvature) such as oleic acid (OA). Although the data obtained have been consistent with the lipid stalk model, alternative explanations have also been discussed that relate to an influence of these lipids on the interaction of the fusion peptides with the target membrane (17,18,32,37,49). …”

supporting

confidence: 66%

“…Modification of the lipid composition of the target membrane, however, can also have an influence on the initial interaction with fusion peptides or other structural elements of fusion proteins that are required for driving fusion (17,18,32,37,49). They can also potentially affect the way the fusion peptide is inserted into the membrane, thereby modifying local membrane disruptions that are required for promoting fusion (37).…”

Section: Discussionmentioning

confidence: 99%

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Effect of Membrane Curvature-Modifying Lipids on Membrane Fusion by Tick-Borne Encephalitis Virus

Stiasny

Heinz

2004

J Virol

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Enveloped viruses enter cells by fusion of their own membrane with a cellular membrane. Incorporation of inverted-cone-shaped lipids such as lysophosphatidylcholine (LPC) into the outer leaflet of target membranes has been shown previously to impair fusion mediated by class I viral fusion proteins, e.g., the influenza virus hemagglutinin. It has been suggested that these results provide evidence for the stalk-pore model of fusion, which involves a hemifusion intermediate (stalk) with highly bent outer membrane leaflets. Here, we investigated the effect of inverted-cone-shaped LPCs and the cone-shaped oleic acid (OA) on the membrane fusion activity of a virus with a class II fusion protein, the flavivirus tick-borne encephalitis virus (TBEV). This study included an analysis of lipid mixing, as well as of the steps preceding or accompanying fusion, i.e., binding to the target membrane and lipid-induced conformational changes in the fusion protein E. We show that the presence of LPC in the outer leaflet of target liposomes strongly inhibited TBEV-mediated fusion, whereas OA caused a very slight enhancement, consistent with a fusion mechanism involving a lipid stalk. However, LPC also impaired the low-pH-induced binding of a soluble form of the E protein to liposomes and its conversion into a trimeric postfusion structure that requires membrane binding at low pH. Because inhibition is already observed before the lipid-mixing step, it cannot be determined whether impairment of stalk formation is a contributing factor in the inhibition of fusion by LPC. These data emphasize, however, the importance of the composition of the target membrane in its interactions with the fusion peptide that are crucial for the initiation of fusion.Fusion of viral membranes with cellular membranes is a key step in the entry of enveloped viruses into cells. It requires energy to overcome repulsive forces between the opposing membranes and to locally disrupt the original lipid bilayer structures. This energy is provided by structural changes and protein-protein, as well as protein-lipid, interactions of specific viral envelope proteins, designated viral fusion proteins. In infectious virions these proteins exist in a metastable state and respond to a specific fusion trigger (receptor binding or acidic pH) by conformational changes that lead to the exposure of the fusion peptide and the formation of an energetically more stable postfusion structure (23,25,49). So far, two structurally different classes of viral fusion proteins have been identified (30). Class I is represented by the spike-like envelope proteins found in orthomyxo-, paramyxo-, retro-, filo-, and coronaviruses. They are characterized by amino-terminal or amino-proximal fusion peptides, as well as the formation of a hairpin-like postfusion structure with a central trimeric coiled coil. In this postfusion form the membraneinserted N and C termini are located at the same end of a very stable protein rod (11, 51). The class II fusion proteins of flaviviruses and alphaviruses are c...

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supporting

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Effect of Membrane Curvature-Modifying Lipids on Membrane Fusion by Tick-Borne Encephalitis Virus

Stiasny

Heinz

2004

J Virol

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“…Indeed, by disrupting the integrity and permeability of the cell membrane, lysophospholipids induce changes in the conformation and activity of numerous membrane proteins, e.g. ion channels (57). If TgLCAT forms lysophospholipids within the PV membrane, the concentration of these lipids in this membrane may result in local membranous injuries and increases in PV membrane permeability, allowing the passage of molecules/ions that may subsequently activate downstream effectors required for egress, such as TgPLP1.…”

Section: Discussionmentioning

confidence: 99%

A Lipolytic Lecithin:Cholesterol Acyltransferase Secreted by Toxoplasma Facilitates Parasite Replication and Egress

Pszenny

Ehrenman

Romano

et al. 2016

Journal of Biological Chemistry

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The protozoan parasite Toxoplasma gondii develops within a parasitophorous vacuole (PV) in mammalian cells, where it scavenges cholesterol. When cholesterol is present in excess in its environment, the parasite expulses this lipid into the PV or esterifies it for storage in lipid bodies. Here, we characterized a unique T. gondii homologue of mammalian lecithin:cholesterol acyltransferase (LCAT), a key enzyme that produces cholesteryl esters via transfer of acyl groups from phospholipids to the 3-OH of free cholesterol, leading to the removal of excess cholesterol from tissues. TgLCAT contains a motif characteristic of serine lipases "AHSLG" and the catalytic triad consisting of serine, aspartate, and histidine (SDH) from LCAT enzymes. TgL-CAT is secreted by the parasite, but unlike other LCAT enzymes it is cleaved into two proteolytic fragments that share the residues of the catalytic triad and need to be reassembled to reconstitute enzymatic activity. TgLCAT uses phosphatidylcholine as substrate to form lysophosphatidylcholine that has the potential to disrupt membranes. The released fatty acid is transferred to cholesterol, but with a lower transesterification activity than mammalian LCAT. TgLCAT is stored in a subpopulation of dense granule secretory organelles, and following secretion, it localizes to the PV and parasite plasma membrane. LCAT-null parasites have impaired growth in vitro, reduced virulence in animals, and exhibit delays in egress from host cells. Parasites overexpressing LCAT show increased virulence and faster egress. These observations demonstrate that TgLCAT influences the outcome of an infection, presumably by facilitating replication and egress depending on the developmental stage of the parasite.The phospholipase A 2 (PLA 2 ) 2 family of serine lipases comprises more than 30 enzymes in mammals. The PLA 2 members hydrolyze the sn-2 ester of phospholipids, yielding lysophospholipid and releasing a fatty acid (1). Approximately one-third of the PLA 2 family members are secreted from cells and display various localizations post-secretion, reflecting their specialized biological functions (2). Among the secretory PLA 2 , lecithin: cholesterol acyltransferase (LCAT; EC 2.3.1.43) is characterized by dual activity, PLA 2 and acyltransferase. In mammals, this enzyme catalyzes the transacylation of the sn-2 fatty acid liberated from various phospholipids (e.g. phosphatidylcholine or phosphatidylethanolamine) to the 3-␤-hydroxyl group on the A-ring of cholesterol, thereby forming cholesteryl esters (3-5). The primary sequence of LCAT is well conserved between mammalian species (6). A structural model for LCAT predicts the conformation of a catalytic triad formed by SerAsp-His residues involved in the phospholipase reaction (7). Mammalian LCATs are primarily expressed in the liver and secreted to the plasma where they circulate in association with HDL (8). These enzymes are components of the reverse cholesterol transport pathway by which cholesterol from peripheral cells is delivered to the liver f...

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“…Furthermore, several antimicrobial peptides that disrupt lipid membranes have a sheet-loopsheet or helix-loop-helix structure (2,3). Differences in the depth and/or angle of insertion of these membrane-invasive structures into the lipid bilayer may dictate the outcome (i.e., lysis, fusion, or no effect) of the membrane interaction (35,41,42,55). Mutational analysis clearly revealed that the p10 ectodomain CR influences syncytium formation, suggesting that this region might influence the folding or function of the p10 HP.…”

Section: Vol 78 2004 Reovirus Fusion Peptide 2815mentioning

confidence: 99%

Structural and Functional Properties of an Unusual Internal Fusion Peptide in a Nonenveloped Virus Membrane Fusion Protein

Shmulevitz

Epand

et al. 2004

J Virol

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The avian and Nelson Bay reoviruses are two of only a limited number of nonenveloped viruses capable of inducing cell-cell membrane fusion. These viruses encode the smallest known membrane fusion proteins (p10). We now show that a region of moderate hydrophobicity we call the hydrophobic patch (HP), present in the small N-terminal ectodomain of p10, shares the following characteristics with the fusion peptides of enveloped virus fusion proteins: (i) an abundance of glycine and alanine residues, (ii) a potential amphipathic secondary structure, (iii) membrane-seeking characteristics that correspond to the degree of hydrophobicity, and (iv) the ability to induce lipid mixing in a liposome fusion assay. The p10 HP is therefore predicted to provide a function in the mechanism of membrane fusion similar to those of the fusion peptides of enveloped virus fusion peptides, namely, association with and destabilization of opposing lipid bilayers. Mutational and biophysical analysis suggested that the internal fusion peptide of p10 lacks alpha-helical content and exists as a disulfidestabilized loop structure. Similar kinked structures have been reported in the fusion peptides of several enveloped virus fusion proteins. The preservation of a predicted loop structure in the fusion peptide of this unusual nonenveloped virus membrane fusion protein supports an imperative role for a kinked fusion peptide motif in biological membrane fusion.The physical properties of phospholipid bilayers impose an energy barrier to spontaneous membrane fusion, thereby maintaining the compartmentalized nature of cells (48, 61). Nonetheless, regulated membrane merger is an essential cellular process. Cellular fusion proteins facilitate membrane merger for diverse processes, including intracellular vesicle transport and the formation of zygotes, multinucleated myotubes, and osteoclasts (44,58,59). Furthermore, the entry of all enveloped viruses involves membrane fusion induced by viral fusion proteins (29,52,58). Understanding the mechanisms of membrane fusion mediated by proteins from diverse sources, therefore, has broad implications.The best-characterized fusion proteins are those involved in the entry of enveloped viruses. The fusion machinery of enveloped viruses frequently consists of a single large multimeric protein (18,50). A hallmark feature of enveloped viral fusion proteins is the presence of two hydrophobic sequences, the transmembrane (TM) domain and the fusion peptide, that simultaneously anchor the protein in both the donor and target membranes (58). Numerous studies have demonstrated the significance of enveloped virus fusion peptides in destabilizing target membranes and favoring membrane merger (17, 25). Fusion peptides are short membrane-seeking motifs that frequently assume helical structures in association with membranes. These fusion peptides lie sequestered within the tertiary structure of the prefusion conformation of the fusion protein. Fusion protein activation follows receptor binding-or low pH-induced remodeling of th...

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Lysophosphatidylcholine mediates the mode of insertion of the NH₂‐terminal SIV fusion peptide into the lipid bilayer

Cited by 30 publications

References 34 publications

Effect of Membrane Curvature-Modifying Lipids on Membrane Fusion by Tick-Borne Encephalitis Virus

Effect of Membrane Curvature-Modifying Lipids on Membrane Fusion by Tick-Borne Encephalitis Virus

A Lipolytic Lecithin:Cholesterol Acyltransferase Secreted by Toxoplasma Facilitates Parasite Replication and Egress

Structural and Functional Properties of an Unusual Internal Fusion Peptide in a Nonenveloped Virus Membrane Fusion Protein

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Lysophosphatidylcholine mediates the mode of insertion of the NH2‐terminal SIV fusion peptide into the lipid bilayer

Cited by 30 publications

References 34 publications

Effect of Membrane Curvature-Modifying Lipids on Membrane Fusion by Tick-Borne Encephalitis Virus

Effect of Membrane Curvature-Modifying Lipids on Membrane Fusion by Tick-Borne Encephalitis Virus

A Lipolytic Lecithin:Cholesterol Acyltransferase Secreted by Toxoplasma Facilitates Parasite Replication and Egress

Structural and Functional Properties of an Unusual Internal Fusion Peptide in a Nonenveloped Virus Membrane Fusion Protein

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Lysophosphatidylcholine mediates the mode of insertion of the NH₂‐terminal SIV fusion peptide into the lipid bilayer