Lessons from a Single Amino Acid Substitution: Anticancer and Antibacterial Properties of Two Phospholipase A2-Derived Peptides

Abstract

The membrane-active nature of phospholipase A2-derived peptides makes them potential candidates for antineoplastic and antibacterial therapies. Two short 13-mer C-terminal fragments taken from snake venom Lys49-PLA2 toxins (p-AppK and p-Acl), differing by a leucine/phenylalanine substitution, were synthesized and their bioactivity was evaluated. Their capacity to interfere with the survival of Gram-positive and Gram-negative bacteria as well as with solid and liquid tumors was assessed in vitro. Toxicity to red blood cells was investigated via in silico and in vitro techniques. The mode of action was mainly studied by molecular dynamics simulations and membrane permeabilization assays. Briefly, both peptides have dual activity, i.e., they act against both bacteria, including multidrug-resistant strains and tumor cells. All tested bacteria were susceptible to both peptides, Pseudomonas aeruginosa being the most affected. RAMOS, K562, NB4, and CEM cells were the main leukemic targets of the peptides. In general, p-Acl showed more significant activity, suggesting that phenylalanine confers advantages to the antibacterial and antitumor mechanism, particularly for osteosarcoma lines (HOS and MG63). Peptide-based treatment increased the uptake of a DNA-intercalating dye by bacteria, suggesting membrane damage. Indeed, p-AppK and p-Acl did not disrupt erythrocyte membranes, in agreement with in silico predictions. The latter revealed that the peptides deform the membrane and increase its permeability by facilitating solvent penetration. This phenomenon is expected to catalyze the permeation of solutes that otherwise could not cross the hydrophobic membrane core. In conclusion, the present study highlights the role of a single amino acid substitution present in natural sequences towards the development of dual-action agents. In other words, dissecting and fine-tuning biomembrane remodeling proteins, such as snake venom phospholipase A2 isoforms, is again demonstrated as a valuable source of therapeutic peptides.

Malaysian and Chinese King Cobra Venom Cytotoxicity in Melanoma and Neonatal Foreskin Fibroblasts Is Mediated by Age and Geography

“…Chemically synthesised compounds could be further optimised for their efficacy and safety and could therefore set the foundations for the next generation of anticancer drug candidates. Promising examples of such toxins targeting various tumor cells are reported in the literature, including peptides inspired from Lys49 phospholipase A2 snake venoms [ 31 , 32 , 33 ].…”

Traditional and Computational Screening of Non-Toxic Peptides and Approaches to Improving Selectivity

“…They are very particular cells, as they lack a nucleus and organelles with a membrane inside [ 60 ]. One can put into question the validity of their use as a standard and valuable in vitro model for cytotoxicity assessment [ 61 ], which is justified by their abundance in organisms, easy cultivation, and availability in significant amounts [ 54 ]. The isolation and cultivation of other cell types often present higher complexity, i.e., rat intestinal epithelial cells and human umbilical vein endothelial cells [ 62 ] or the use of mice-derived macrophages [ 9 ].…”

Molecules at Play in Cancer

“…Although most of these studies were carried out on human samples, two groups, Somlyai et al [ 12 ] and Gutierez et al [ 16 ], used mouse models, while Almeida et al [ 23 ] tested the proposed solutions on bacteria. A comprehensive review by Lucio et al [ 24 ] presents the major accomplishments in cancer research that have been possible by the use of the nematode Caenorhaditis elegans .…”