Optical Microscopy of Giant Vesicles as a Tool to Reveal the Mechanism of Action of Antimicrobial Peptides and the Specific Case of Gomesin

Riske, Karin A.

doi:10.1016/bs.adplan.2014.12.001

Cited by 18 publications

(20 citation statements)

References 101 publications

(150 reference statements)

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“…Similar observations have been made before for daptomycin (14) and mastoparans (37). It could be argued that these areas represent folds of the bilayer (37, 38), lipid–peptide aggregates on the membrane (14), or nonbilayer structures. Huang and coworkers (14) observed a change in the area of the GUV membrane upon interaction with daptomycin: the area of the GUV membrane first expands by ≈ 4% and then contracts to an area ≈ 1% smaller than the original membrane area (14).…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…Those regions have been interpreted as folds, or invaginations, of the membrane, where a bilayer patch slides over the main surface of the GUV membrane (37, 38). In addition, membrane deformations have been reported, for example in the cases of mastoparans and gomesin (37, 38, 52), in which a portion of the membrane protrudes, or the entire GUV significantly changes shape. We have noticed such deformations as well with several of the α -helical, amphipathic, membrane-active peptides we have studied in GUVs (26, 51), but we have not examined those deformations systematically.…”

Section: Discussionmentioning

confidence: 99%

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Daptomycin–Phosphatidylglycerol Domains in Lipid Membranes

2017

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Daptomycin is an acidic, 13-amino acid, cyclic polypeptide that contains a number of non-proteinogenic residues and is modified at its N-terminus with a decanoyl chain. It has been in clinical use since 2003 against selected drug-resistant Staphylococcus aureus and Enterococcus spp infections. In vitro, daptomycin is active against Gram-positive pathogens at low concentrations but its antibiotic activity depends critically on the presence of calcium ions. This dependence has been thought to arise from binding of one or two Ca2+ ions to daptomycin as a required step in its interaction with the bacterial membrane. Here, we investigated the interaction of daptomycin with giant unilamellar vesicles (GUVs) composed 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and 1-palmitoyl-2-oleoylphosphatidylglycerol (POPG). We used fluorescence confocal microscopy to monitor binding of the peptide to GUVs and follow its effect on the membrane of the vesicle. We found that, in the absence of POPG or Ca2+, daptomycin does not bind measurably to the lipid membrane. In the presence of 20–30% PG in the membrane and 2 mM Ca2+, daptomycin induces the formation of membrane domains rich in acidic lipids. This effect is not induced by Ca2+ alone. In addition, daptomycin causes GUV collapse, but it does not translocate across the membrane to the inside of intact POPC:POPG vesicles. We conclude that pore formation is probably not the mechanism by which the peptide functions. On the other hand, we found that daptomycin coclusters with the anionic phospholipid POPG and the fluorescent probes used, leading to extensive formation of daptomycin–POPG domains in the membrane.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Daptomycin–Phosphatidylglycerol Domains in Lipid Membranes

2017

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“…Giant unilamellar vesicles (GUVs) can be formed either by spontaneous formation (Akashi et al 1996) or by electroformation (Angelova and Dimitrov 1986), and have been extensively reviewed in the literature (Yamazaki and Tamba 2005;Dimova et al 2006;Riske 2015). Briefly, in spontaneous formation, after the solvent has been completely removed by vacuum, the lipid film, whether or not it contains fluorescently labeled lipid, is pre-hydrated with a very small volume of water (~10 μl) at 45°C for a short time,~10 min.…”

Section: Model Membranes and Strategies For Investigating Lipid-packimentioning

confidence: 99%

Lipid-packing perturbation of model membranes by pH-responsive antimicrobial peptides

2017

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The indiscriminate use of conventional antibiotics is leading to an increase in the number of resistant bacterial strains, motivating the search for new compounds to overcome this challenging problem. Antimicrobial peptides, acting only in the lipid phase of membranes without requiring specific membrane receptors as do conventional antibiotics, have shown great potential as possible substituents of these drugs. These peptides are in general rich in basic and hydrophobic residues forming an amphipathic structure when in contact with membranes. The outer leaflet of the prokaryotic cell membrane is rich in anionic lipids, while the surface of the eukaryotic cell is zwitterionic. Due to their positive net charge, many of these peptides are selective to the prokaryotic membrane. Notwithstanding this preference for anionic membranes, some of them can also act on neutral ones, hampering their therapeutic use. In addition to the electrostatic interaction driving peptide adsorption by the membrane, the ability of the peptide to perturb lipid packing is of paramount importance in their capacity to induce cell lysis, which is strongly dependent on electrostatic and hydrophobic interactions. In the present research, we revised the adsorption of antimicrobial peptides by model membranes as well as the perturbation that they induce in lipid packing. In particular, we focused on some peptides that have simultaneously acidic and basic residues. The net charges of these peptides are modulated by pH changes and the lipid composition of model membranes. We discuss the experimental approaches used to explore these aspects of lipid membranes using lipid vesicles and lipid monolayer as model membranes.

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“…LUVs can be prepared by the extrusion method [66,67]. GUVs are formed either by electroformation method according to the method introduced by Angelova et al [68] and extensively revised by Riske et al [69,70], or by the spontaneous swelling method described by Reeves and Dowben [71], improved by Akashi et al [72], and revised by Tamba et al [73][74][75][76].…”

Section: Model Membranesmentioning

confidence: 99%