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Published on: February 14, 2018
Cm-p5, a molluscan-derived antifungal peptide exerts its activity by a membrane surface covering in a non-penetrating
M Gonzalez-Garcia1, B Bertrand2, E M Martell-Huguet1
1Centro de Estudios de Proteínas, Facultad de Biología, Universidad de La Habana, 25th st No 455, Vedado, Plaza, Havana 10400, Cuba.
Abstract:
Amidst the health crisis caused by the rise of multi-resistant pathogenic microorganisms, Antimicrobial Peptides (AMPs) have emerged as a potential alternative to traditional antibiotics. In this sense, Cm-p5 is an AMP with fungistatic activity against the yeast Candida albicans. Its antimicrobial activity and selectivity have been well characterized; however, the mechanism of action is still unknown. This study used biophysical approaches to gain insight into how this peptide exerts its activity. Stability and fluidity of lipid membrane were explored by liposome leakage and Laurdan generalized polarization (GP) respectively, suggesting that Cm-p5 does not perturb lipid membranes even at very high concentrations (≥100 µm.L-1). Likewise, no depolarizing action was observed using 3,3'-propil-2,2'-thyodicarbocianine, a potential membrane fluorescent reporter, with C. albicans cells or the corresponding liposome models. Changes in liposome size were analyzed by Dynamic Light Scattering (DLS) data, indicating that Cm-p5 covers the vesicular surface slightly increasing liposome hydrodynamic size, without liposome rupture. These results were further corroborated with Langmuir monolayer isotherms, where no significant changes in lateral pressure or area per lipid were detected, indicating little or no insertion. Finally, data obtained from molecular dynamics simulations aligned with in vitro observations, whereby Cm-p5 slightly interacted with the fungal membrane model surface without causing significant perturbation. These results suggest Cm-p5 is not a pore-forming anti-fungal peptide and that other mechanisms of action on the membrane as some limitation of fungal nutrition or receptor-dependent transduction for depressing growth development should be explored.
Insights
Antimicrobial peptide Cm-p5 shows fungistatic activity against Candida albicans. Biophysical studies indicate Cm-p5 does not disrupt fungal membranes, suggesting a non-pore-forming mechanism of action.
Area of Science:
- Microbiology
- Biophysics
- Medicinal Chemistry
Background:
- Antimicrobial Peptides (AMPs) are promising alternatives to antibiotics due to rising multi-resistant pathogens.
- The antifungal peptide Cm-p5 exhibits fungistatic activity against Candida albicans, but its mechanism remains unclear.
- Understanding AMP mechanisms is crucial for developing new antifungal therapies.
Purpose of the Study:
- To elucidate the mechanism of action of the antifungal peptide Cm-p5 against Candida albicans.
- To investigate the interaction of Cm-p5 with fungal lipid membranes using biophysical techniques.
- To determine if Cm-p5 perturbs membrane stability, fluidity, or integrity.
Main Methods:
- Liposome leakage assays to assess membrane stability.
- Laurdan generalized polarization (GP) to measure membrane fluidity.
- Fluorescent reporter assays (3,3'-dipropylthiadicarbocyanine iodide) to detect membrane depolarization.
- Dynamic Light Scattering (DLS) to analyze liposome size changes.
- Langmuir monolayer isotherms to study peptide-membrane interactions.
- Molecular dynamics (MD) simulations to model peptide-membrane interactions.
Main Results:
- Cm-p5 did not perturb lipid membranes or cause leakage, even at high concentrations.
- No membrane depolarization was observed in Candida albicans cells or liposomes.
- DLS and Langmuir isotherms indicated Cm-p5 slightly covers the membrane surface without significant insertion or rupture.
- MD simulations corroborated in vitro findings, showing minimal interaction and perturbation of the fungal membrane model.
- Results suggest Cm-p5 is not a pore-forming peptide.
Conclusions:
- Cm-p5 does not exert its fungistatic effect by forming pores or significantly disrupting the fungal membrane.
- Alternative mechanisms, such as nutrient limitation or receptor-mediated signaling, should be investigated for Cm-p5's mode of action.
- Further research into non-pore-forming AMPs like Cm-p5 is warranted for novel antifungal drug development.
