SAR Study of the Human Host-Defence Peptide LL-37: the tools used in our approach

Описание: The studies on structure and mechanism of action of Antimicrobial Peptides (AMPs) are carried out using some tools, such as computational analysis, peptide synthesizer and spectroscopic techniques. Here, we report our approach adopted on the study of primate cathelicidins.

Antimicrobial peptides are an important component of innate immunity that act as a first line of defence against the occurrence of infections. Among these natural antibiotics, those of the cathelicidin family, which includes LL-37 in humans and RL-37 in the primate Macaca mulatta, are intensively studied because of their diverse properties. For example, LL -37 is capable of adopting an amphipathic helical structure in physiological solutions and then oligomerizing; RL-37, on the other hand, remains monomeric and disordered under the same conditions.

The occurrence of intramolecular salt bridges could play an important role in determining the particular structure which is adopted. These important structural aspects are highlighted by predictive applications, allowing us to identify a new stabilized analogue of RL-37 or destabilized analogues of LL -37 to probe positional effects in their sequences underlying their structural behavior. We were able to evaluate the effect on structural stability by monitoring thermal denaturation in plasma mimetic buffer, using circular dichroism assays. These data were compared with functional assays of efficacy against bacterial cells or cytotoxicity to host immune cells.

Selected analogues were also evaluated for the mechanism of antimicrobial action monitoring permeabilization of bacterial membranes to fluorescent probes and other roles in immunity, such as cytotoxicity towards, or triggering of proinflammatory M1 macrophages. These studies have shown a direct correlation between the structure and behavior of the peptides in terms of their direct antimicrobial and host-mediated activity.

Speaker: Andrea Caporale, CNR - IC