• “Effects of cationic AMP 6.2 on membrane fluidity: Implications on the permeabilization

MATURANA PATRICIA; MONTICHI GUILLERMO; MAFFIA, PAULO; HOLLMANN AXEL

Córdoba

Congreso; LI Reunión Anual de la Sociedad Argentina de Biofísica; 2023

Sociedad Argentina de Biofisica

Antibiotic resistance is an increasingly severe health problem. Antimicrobial peptides (AMPs) are being developed in order to overcome this problem due to their broad spectrum of antimicrobial activity and their low capacity to induce resistance in bacteria.In this work using the antimicrobial peptide 6.2 (p6.2), we aimed to study the effect that this peptide induces in the membrane phase transition (Tm) of model membranes by using differential scanning calorimetry (DSC) and dynamic light scattering (DLS) and correlate these changes with membrane permeability evaluated by carboxyfluoresein (CF) leakage experiments. As model membranes, we chose two simple models: one composed of pure DMPC as a mammalian model and a mix of DMPC:DMPG (5:1) as a bacterial model membrane.First, by DLS we obtain the Tm of both lipid compositions used, and evaluate the effect of p6.2 addition. Our results showed that on pure DMPC membrane, no significant changes were observed. On the other hand, in the case of DMPC:DMPG membranes, an increase in the Tm value, dependent on peptide concentration, was observed.Then, the DSC calorimetric profiles for both lipid formulations were obtained. For pure DMPC, a symmetric and highly cooperative peak was observed; when we added p6.2, the Tm did not undergo significant changes, in good agreement with DLS data. The constant values observed would indicate that p6.2 does not perturb the hydrocarbon chain packing of DMPC. While for DMPC:DMPG membranes, the addition of p6.2, results in a much distorted DSC profile with asymmetric peaks, which could be related to a massive alteration of the membrane structure.Finally, the ability of p6.2 to disrupt the membrane was evaluated for both lipid formulations tested. We observed that p6.2 induces a higher leakage of CF on DMPC:DMPG liposomes even at lower concentrations and also exhibited faster leakage kinetics than for pure DMPC liposomes.Overall, these results indicate that the interaction of p6.2 with DMPC:DMPG lipid membranes changes the fluidity of the bilayer to a more rigid system. In this sense, the interaction of p6.2 with the lipids could induce more rigid lipid-peptide domains that could destabilize the bilayer, inducing an efficient leakage of CF on the boundaries of those domains.