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Structural and antimicrobial properties of human pre-elafin/trappin-2 and derived peptides against Pseudomonas aeruginosa.

Bellemare A, Vernoux N, Morin S, Gagné SM, Bourbonnais Y - BMC Microbiol. (2010)

Bottom Line: The N-terminal cementoin domain adopts α-helical secondary structures in a membrane mimetic environment, which is common in antimicrobial peptides.However, unlike numerous linear polycationic antimicrobial peptides, membrane disruption does not appear to be the main function of either cementoin, elafin or full-length pre-elafin/trappin-2 against P. aeruginosa.Our results rather suggest that pre-elafin/trappin-2 and elafin, but not cementoin, possess the ability to modulate the expression of some P.aeruginosa virulence factors, possibly through acting on intracellular targets.

View Article: PubMed Central - HTML - PubMed

Affiliation: Département de Biochimie, Microbiologie et Bio-informatique, Institut de Biologie Intégrative et des Systèmes and Regroupement PROTEO, Université Laval, Québec, Canada.

ABSTRACT

Background: Pre-elafin/trappin-2 is a human innate defense molecule initially described as a potent inhibitor of neutrophil elastase. The full-length protein as well as the N-terminal "cementoin" and C-terminal "elafin" domains were also shown to possess broad antimicrobial activity, namely against the opportunistic pathogen P. aeruginosa. The mode of action of these peptides has, however, yet to be fully elucidated. Both domains of pre-elafin/trappin-2 are polycationic, but only the structure of the elafin domain is currently known. The aim of the present study was to determine the secondary structures of the cementoin domain and to characterize the antibacterial properties of these peptides against P. aeruginosa.

Results: We show here that the cementoin domain adopts an α-helical conformation both by circular dichroism and nuclear magnetic resonance analyses in the presence of membrane mimetics, a characteristic shared with a large number of linear polycationic antimicrobial peptides. However, pre-elafin/trappin-2 and its domains display only weak lytic properties, as assessed by scanning electron micrography, outer and inner membrane depolarization studies with P. aeruginosa and leakage of liposome-entrapped calcein. Confocal microscopy of fluorescein-labeled pre-elafin/trappin-2 suggests that this protein possesses the ability to translocate across membranes. This correlates with the finding that pre-elafin/trappin-2 and elafin bind to DNA in vitro and attenuate the expression of some P. aeruginosa virulence factors, namely the biofilm formation and the secretion of pyoverdine.

Conclusions: The N-terminal cementoin domain adopts α-helical secondary structures in a membrane mimetic environment, which is common in antimicrobial peptides. However, unlike numerous linear polycationic antimicrobial peptides, membrane disruption does not appear to be the main function of either cementoin, elafin or full-length pre-elafin/trappin-2 against P. aeruginosa. Our results rather suggest that pre-elafin/trappin-2 and elafin, but not cementoin, possess the ability to modulate the expression of some P.aeruginosa virulence factors, possibly through acting on intracellular targets.

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Related in: MedlinePlus

Depolarization of P. aeruginosa membranes upon incubation with magainin 2, pre-elafin/trappin-2 or derived peptides. Fluorescence emission (arbitrary units) of the probe NPN inserted into the outer membrane (top panel) or the probe DiSC3 inserted into the inner membrane (bottom panel) of P. aeruginosa upon addition of the indicated peptides. The controls were performed in phosphate buffer alone. Pre-elafin/trappin-2 and elafin were used at 20 μM, cementoin at 100 μM and magainin 2 at 10 μM. The arrow indicates the time-point for the addition of the various peptides.
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Figure 3: Depolarization of P. aeruginosa membranes upon incubation with magainin 2, pre-elafin/trappin-2 or derived peptides. Fluorescence emission (arbitrary units) of the probe NPN inserted into the outer membrane (top panel) or the probe DiSC3 inserted into the inner membrane (bottom panel) of P. aeruginosa upon addition of the indicated peptides. The controls were performed in phosphate buffer alone. Pre-elafin/trappin-2 and elafin were used at 20 μM, cementoin at 100 μM and magainin 2 at 10 μM. The arrow indicates the time-point for the addition of the various peptides.

Mentions: To further document that membrane disruption may not be the primary role of cementoin, elafin and pre-elafin/trappin-2, the ability of these peptides to cause membrane depolarization using the fluorescent probes, 1-N-phenylnaphthylamine (NPN) and 3,3'- dipropylthiacarbocyanine (DiSC3) was tested. NPN is a neutral hydrophobic probe that is excluded by an intact outer membrane, but is taken up into the membrane interior of an outer membrane that is disrupted by antimicrobial peptide action [34]. NPN fluoresces weakly in free solution but strongly when it crosses the outer membrane barrier into the cell. As shown in Fig. 3 (top panel), upon addition of 10 μM magainin 2 a sharp increase in fluorescence was observed. The addition of 20 μM pre-elafin/trappin-2 led to a much weaker fluorescence signal, and 100 μM cementoin or 20 μM elafin had no effects on membrane depolarization. No variation of fluorescence was seen upon addition of NPN to bacterial cells when no peptide was added. To evaluate the effects of the recombinant peptides on P. aeruginosa cytoplasmic membrane, the fluorescent probe DiSC3 was used. DiSC3 distributes between the cells and the medium. This cationic dye concentrates in the cytoplasmic membrane under the influence of the membrane potential resulting in a self-quenching of fluorescence. If the membrane is depolarized, the probe will be released into the medium, causing a measurable increase in fluorescence [35]. The assays were again compared with magainin 2, which can permeabilize the bacterial membranes. In contrast to a strong release of fluorescence upon addition of magainin 2, pre-elafin/trappin-2 and derived peptides weakly, if at all, induced fluorescence emission (Fig. 3; bottom panel). Our results suggest that pre-elafin/trappin-2 and derived peptides, in contrast to magainin 2, acted on the outer and inner membranes without causing extensive membrane depolarization.


Structural and antimicrobial properties of human pre-elafin/trappin-2 and derived peptides against Pseudomonas aeruginosa.

Bellemare A, Vernoux N, Morin S, Gagné SM, Bourbonnais Y - BMC Microbiol. (2010)

Depolarization of P. aeruginosa membranes upon incubation with magainin 2, pre-elafin/trappin-2 or derived peptides. Fluorescence emission (arbitrary units) of the probe NPN inserted into the outer membrane (top panel) or the probe DiSC3 inserted into the inner membrane (bottom panel) of P. aeruginosa upon addition of the indicated peptides. The controls were performed in phosphate buffer alone. Pre-elafin/trappin-2 and elafin were used at 20 μM, cementoin at 100 μM and magainin 2 at 10 μM. The arrow indicates the time-point for the addition of the various peptides.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2958999&req=5

Figure 3: Depolarization of P. aeruginosa membranes upon incubation with magainin 2, pre-elafin/trappin-2 or derived peptides. Fluorescence emission (arbitrary units) of the probe NPN inserted into the outer membrane (top panel) or the probe DiSC3 inserted into the inner membrane (bottom panel) of P. aeruginosa upon addition of the indicated peptides. The controls were performed in phosphate buffer alone. Pre-elafin/trappin-2 and elafin were used at 20 μM, cementoin at 100 μM and magainin 2 at 10 μM. The arrow indicates the time-point for the addition of the various peptides.
Mentions: To further document that membrane disruption may not be the primary role of cementoin, elafin and pre-elafin/trappin-2, the ability of these peptides to cause membrane depolarization using the fluorescent probes, 1-N-phenylnaphthylamine (NPN) and 3,3'- dipropylthiacarbocyanine (DiSC3) was tested. NPN is a neutral hydrophobic probe that is excluded by an intact outer membrane, but is taken up into the membrane interior of an outer membrane that is disrupted by antimicrobial peptide action [34]. NPN fluoresces weakly in free solution but strongly when it crosses the outer membrane barrier into the cell. As shown in Fig. 3 (top panel), upon addition of 10 μM magainin 2 a sharp increase in fluorescence was observed. The addition of 20 μM pre-elafin/trappin-2 led to a much weaker fluorescence signal, and 100 μM cementoin or 20 μM elafin had no effects on membrane depolarization. No variation of fluorescence was seen upon addition of NPN to bacterial cells when no peptide was added. To evaluate the effects of the recombinant peptides on P. aeruginosa cytoplasmic membrane, the fluorescent probe DiSC3 was used. DiSC3 distributes between the cells and the medium. This cationic dye concentrates in the cytoplasmic membrane under the influence of the membrane potential resulting in a self-quenching of fluorescence. If the membrane is depolarized, the probe will be released into the medium, causing a measurable increase in fluorescence [35]. The assays were again compared with magainin 2, which can permeabilize the bacterial membranes. In contrast to a strong release of fluorescence upon addition of magainin 2, pre-elafin/trappin-2 and derived peptides weakly, if at all, induced fluorescence emission (Fig. 3; bottom panel). Our results suggest that pre-elafin/trappin-2 and derived peptides, in contrast to magainin 2, acted on the outer and inner membranes without causing extensive membrane depolarization.

Bottom Line: The N-terminal cementoin domain adopts α-helical secondary structures in a membrane mimetic environment, which is common in antimicrobial peptides.However, unlike numerous linear polycationic antimicrobial peptides, membrane disruption does not appear to be the main function of either cementoin, elafin or full-length pre-elafin/trappin-2 against P. aeruginosa.Our results rather suggest that pre-elafin/trappin-2 and elafin, but not cementoin, possess the ability to modulate the expression of some P.aeruginosa virulence factors, possibly through acting on intracellular targets.

View Article: PubMed Central - HTML - PubMed

Affiliation: Département de Biochimie, Microbiologie et Bio-informatique, Institut de Biologie Intégrative et des Systèmes and Regroupement PROTEO, Université Laval, Québec, Canada.

ABSTRACT

Background: Pre-elafin/trappin-2 is a human innate defense molecule initially described as a potent inhibitor of neutrophil elastase. The full-length protein as well as the N-terminal "cementoin" and C-terminal "elafin" domains were also shown to possess broad antimicrobial activity, namely against the opportunistic pathogen P. aeruginosa. The mode of action of these peptides has, however, yet to be fully elucidated. Both domains of pre-elafin/trappin-2 are polycationic, but only the structure of the elafin domain is currently known. The aim of the present study was to determine the secondary structures of the cementoin domain and to characterize the antibacterial properties of these peptides against P. aeruginosa.

Results: We show here that the cementoin domain adopts an α-helical conformation both by circular dichroism and nuclear magnetic resonance analyses in the presence of membrane mimetics, a characteristic shared with a large number of linear polycationic antimicrobial peptides. However, pre-elafin/trappin-2 and its domains display only weak lytic properties, as assessed by scanning electron micrography, outer and inner membrane depolarization studies with P. aeruginosa and leakage of liposome-entrapped calcein. Confocal microscopy of fluorescein-labeled pre-elafin/trappin-2 suggests that this protein possesses the ability to translocate across membranes. This correlates with the finding that pre-elafin/trappin-2 and elafin bind to DNA in vitro and attenuate the expression of some P. aeruginosa virulence factors, namely the biofilm formation and the secretion of pyoverdine.

Conclusions: The N-terminal cementoin domain adopts α-helical secondary structures in a membrane mimetic environment, which is common in antimicrobial peptides. However, unlike numerous linear polycationic antimicrobial peptides, membrane disruption does not appear to be the main function of either cementoin, elafin or full-length pre-elafin/trappin-2 against P. aeruginosa. Our results rather suggest that pre-elafin/trappin-2 and elafin, but not cementoin, possess the ability to modulate the expression of some P.aeruginosa virulence factors, possibly through acting on intracellular targets.

Show MeSH
Related in: MedlinePlus