Structural requirements for antimicrobial versus chemoattractant activities for dermaseptin S9

Abstract

Antimicrobial peptides that play a role in host defence against competing or pathogenic microorganisms are small proteins, typically 10-50 residues long, interact with lipid bilayers to alter cell-membrane permeability, which often leads to cell death. Structural studies have revealed that the peptide secondary structures include a-helices, b-sheet structures stabilized by two or three disulfide bonds, and extended structures with overrepresentation of one or two amino acids (W, P, H or G) [1]. However, all these peptides, regardless of the secondary structure or length, are cationic and exhibit amphipathic properties upon interaction with lipid bilayers, with apolar amino acid residues segregating from the hydrophilic residues on opposite sides of the 3D structure. These structural elements are believed to play a crucial role in the binding of cationic host [468][469][470][471][472][473][474][475][476][477][478][479][480] demonstrated that this peptide adopted a non-amphipathic a-helical conformation in trifluoroethanol ⁄ water mixtures, but was highly aggregated in aqueous solutions and in the presence of sodium dodecyl sulfate micelles. Circular dichroism, FTIR and attenuated total reflectance FTIR spectroscopies, combined with a surface plasmon resonance study, show that Drs S9 forms stable and ordered b-sheet aggregates in aqueous buffers or when bound to anionic or zwitterionic phospholipid vesicles. These structures slowly assembled into amyloid-like fibrils in aqueous environments via spherical intermediates, as revealed by electron microscopy and Congo red staining. Drs S9 induced the directional migration of neutrophils, T lymphocytes and monocytes. Interestingly, the antimicrobial and chemotactic activities of Drs S9 are modulated by its amyloid-like properties. Whereas spherical oligomers of Drs S9 exhibit antimicrobial activity, the soluble, weakly selfassociated forms of Drs S9 act on human leukocytes to promote chemotaxis and ⁄ or immunological response activation in the same range of concentration as amyloidogenic peptides Ab(1-42), the most fibrillogenic isoform of amyloid beta peptides, and the prion peptide PrP(106-126).

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

“…Drs S9 has a propensity to form amyloid-like fibrils in solution at high concentration [14], although the aggregation process is found to be slow compared to amyloid peptides, typically requiring several hours at 500 µM [14]. Consistent with this, we observed the formation of fibrils for Drs S9 in solution at 100 µM after 1 day of incubation (Figures 3A-E).…”

“…Consistent with this, previous structural studies showed that Drs S9 folds into an α-helical structure in TFE/water mixtures, while the NMR spectrum in water shows very broad signals indicative of aggregation in aqueous solution [13]. Subsequently, it was shown that Drs S9 slowly assembles into amyloid-like fibrils at 500 µM in aqueous solution and that the antimicrobial and chemotactic activities of Drs S9 are modulated by its propensity to form fibrils [14]. Indeed, Drs S9 exhibited an antimicrobial activity against all Gram-negative bacteria strains tested at day 0 and day 3 whereas the peptide exhibited little or no antibacterial activity after 7 days of incubation.…”

“…This Drs S9/lipid interaction may be important for the antimicrobial activity of the peptide, for example because membranes may modulate the conformation or the fibril forming propensity of the peptide, and/or because the peptide may interfere with the permeability properties of the membrane. Despite this potential biological importance, to our knowledge these two studies [13], [14] are the only ones so far on the interaction between membranes and Drs S9.…”

Exploring New Biological Functions of Amyloids: Bacteria Cell Agglutination Mediated by Host Protein Aggregation

“…However, it is well known that some proteins can accelerate its aggregation kinetics in the presence of membrane-like environments [48]–[50]. Our results show that wtECP is able to form fibrillar-like aggregates on model membranes with an average size of 845±150 nm (Figure 4B), comparable in size with the wtECP aggregates observed in vitro in the absence of lipid membranes (∼150 nm) [28].…”

A peptide from human β thymosin as a platform for the development of new anti-biofilm agents for Staphylococcus spp. and Pseudomonas aeruginosa

“…SP1 MD simulations have shown that Tb4 9-19 has a structure constituted by a central hydrophobic region and by the presence of peripheral charged residues. Another example of non-amphipathic antimicrobial peptide is Dermaseptin S9, produced by the skin of the South American hylid frog, Phyllomedusa sauvagei; this peptide contains, centrally located, a hydrophobic core, with a high affinity toward the bacterial membrane (Lequin et al 2006) and has a microbicidal effect by perturbing the bacterial membrane (Auvynet et al 2008).…”