Biophysical Investigation of the Membrane-Disrupting Mechanism of the Antimicrobial and Amyloid-Like Peptide Dermaseptin S9

Abstract

Dermaseptin S9 (Drs S9) is an atypical cationic antimicrobial peptide with a long hydrophobic core and with a propensity to form amyloid-like fibrils. Here we investigated its membrane interaction using a variety of biophysical techniques. Rather surprisingly, we found that Drs S9 induces efficient permeabilisation in zwitterionic phosphatidylcholine (PC) vesicles, but not in anionic phosphatidylglycerol (PG) vesicles. We also found that the peptide inserts more efficiently in PC than in PG monolayers. Therefore, electrostatic interactions between the cationic Drs S9 and anionic membranes cannot explain the selectivity of the peptide towards bacterial membranes. CD spectroscopy, electron microscopy and ThT fluorescence experiments showed that the peptide adopts slightly more β-sheet and has a higher tendency to form amyloid-like fibrils in the presence of PC membranes as compared to PG membranes. Thus, induction of leakage may be related to peptide aggregation. The use of a pre-incorporation protocol to reduce peptide/peptide interactions characteristic of aggregates in solution resulted in more α-helix formation and a more pronounced effect on the cooperativity of the gel-fluid lipid phase transition in all lipid systems tested. Calorimetric data together with 2H- and 31P-NMR experiments indicated that the peptide has a significant impact on the dynamic organization of lipid bilayers, albeit slightly less for zwitterionic than for anionic membranes. Taken together, our data suggest that in particular in membranes of zwitterionic lipids the peptide binds in an aggregated state resulting in membrane leakage. We propose that also the antimicrobial activity of Drs S9 may be a result of binding of the peptide in an aggregated state, but that specific binding and aggregation to bacterial membranes is regulated not by anionic lipids but by as yet unknown factors.

Mammalian antimicrobial peptide protegrin‐4 self assembles and forms amyloid‐like aggregates: Assessment of its functional relevance

“…It was reported previously that human AMP LL‐37 can naturally oligomerize at physiological pH into nanoparticles to resist the action of proteases . In past years, several studies have reported the self‐assembly phenomenon of AMPs . Our group has previously reported the formation of amyloid‐like assemblies by a plant AMP .…”

Amyloid aggregation and membrane activity of the antimicrobial peptide uperin 3.5

“…Consequently, this study supports the hypothesis that amyloidogenic aggregation of peptides is a pathway that provides active and novel antimicrobials. Potentially, pathological disorders might result from aberrant behaviour or improper regulation of this amyloid‐mediated antimicrobial action …”

“…A beguiling hypothesis is that amyloidogenic peptides are antimicrobial, host‐defense peptides . In accordance with this, amyloidogenic peptides and antimicrobial peptides (AMPs) share the ability to bind to/within a cell membrane inducing a similar permeation (barrel‐stave or toroidal pores) or disruption (carpet or detergent effect) of the membrane, while doing so via potentially different mechanisms .…”

Cm-p5: an antifungal hydrophilic peptide derived from the coastal mollusk Cenchritis muricatus (Gastropoda: Littorinidae)

“…Indeed, the specificity showed by Cm‐p5 is in accordance with its condition to be nontoxic for mammalian cells. It is noteworthy that the antibacterial peptide dermaseptin S9 (similar nonamphipatic pattern regarding Cm‐p5) inserts less efficiently in phosphatidylglycerol than in phosphatidylcholine monolayers (54). This behavior is in contrast with the specificity showed by Cm‐p5.…”