Liposome destabilization induced by synthetic lipopeptides corresponding to envelope and non-structural domains of GBV-C/HGV virus. Conformational requirements for leakage

Endocytosis Is a Key Mode of Interaction between Extracellular β-Amyloid and the Cell Membrane

Interactions between amyloid-β peptide (Aβ) and the cell membrane include interaction with membrane lipids and binding to membrane receptors, both of which are considered to be the toxicity mechanisms of Aβ. However, it is unclear whether both mechanisms lead to cytotoxicity. Thus, we aimed to analyze these two mechanisms of Aβ42 interaction with cell membranes under different Aβ aggregation states. To this end, model membrane experiments were conducted. Quantitative analysis of Aβ42 monomers or oligomers bound to the membrane of neuro-2a cells was also performed, and laser confocal microscopy was employed to assess endocytosis of FITC-Aβ42 monomers or oligomers by neuro-2a cells. We found that the binding capacity of Aβ42 to membrane lipids was weak and that the amount of Aβ42 bound to membrane lipids was low. Moreover, clathrin-mediated endocytosis of Aβ42 oligomers by neuro-2a cells was observed. Endocytosis serves as a key mode of interaction between extracellular Aβ42 and neurons. These findings provide insights into the mechanisms underlying Aβ oligomer metabolism.

Contribution of the Tyr-1 in Plantaricin149a to disrupt phospholipid model membranes

Plantaricin149a (Pln149a) is a cationic antimicrobial peptide, which was suggested to cause membrane destabilization via the carpet mechanism. The mode of action proposed to this antimicrobial peptide describes the induction of an amphipathic α-helix from Ala7 to Lys20, while the N-terminus residues remain in a coil conformation after binding. To better investigate this assumption, the purpose of this study was to determine the contributions of the Tyr1 in Pln149a in the binding to model membranes to promote its destabilization. The Tyr to Ser substitution increased the dissociation constant (KD) of the antimicrobial peptide from the liposomes (approximately three-fold higher), and decreased the enthalpy of binding to anionic vesicles from -17.2 kcal/mol to -10.2 kcal/mol. The peptide adsorption/incorporation into the negatively charged lipid vesicles was less effective with the Tyr1 substitution and peptide Pln149a perturbed the liposome integrity more than the analog, Pln149S. Taken together, the peptide-lipid interactions that govern the Pln149a antimicrobial activity are found not only in the amphipathic helix, but also in the N-terminus residues, which take part in enthalpic contributions due to the allocation at a lipid-aqueous interface.