Enzyme Engineering
Open Access

Abstract

Cytotoxic activity of peptides derived from Parasporin 2Aa1 and its analogs against colon cancer SW480 cells

Jenniffer Cruz

Parasporin-2 (PS2Aa1) is a toxin produced by Bacillus thuringiensis and it has shown a high cytotoxicity against cancer cell lines such as: MOLT-4, Jurkat, Sawano, and HepG2. Accordingly, to explain its cytotoxic effect, a multi-step mechanism model has been proposed: at first, PS2Aa1 would bind to the GPI-anchored receptors or other proteins in the membrane; then, the concentrated toxins oligomerized, after that, transmembrane pores are formed, generating damage into membrane permeability (1). However, its mechanism of action has not been elucidated at all. Therefore, in this research work we carried out a fragmentation of PS2Aa1, synthesizing peptides, by a Fmoc strategy. We obtained 3 peptides derived from different domains of the PS2Aa1 called: P264-G274, Loop1-PS2Aa and Loop2-PS2Aa. Additionally, 3 derivatives of P264-G274 (P264-V268K, P264-V268W, and P264-V268H), 1 derivative of Loop1-PS2Aa (Loop1-Y5K) and 1 derivative of Loop2-PS2Aa (Loop2-N4W) were obtained. Changes in each residue were supported by an increase in the charge and hydrophobicity of the compounds. The secondary structures of the peptides were confirmed by Circular Dichroism (DC) spectra. All the peptides of PS2Aa1 exhibited a secondary structure of α-helix with a maximum absorption band at 190 nm and two minimum absorption bands between 205-220 nm. In addition, the degree of hemolysis of human erythrocytes was determined showing that all the peptides evaluated had an HC₅₀ lower than 100 µM, with less than 24% hemolysis compared to the positive control (TX-100 0.1%). Finally, whole peptides exhibited activity against SW480; highlighting that P264-V268K was the most active with an IC₅₀ of 5.716 μM. 5-fluorouracil, chemotherapy drug, was taken as a positive control. These results clearly demonstrate that P264-V268K has a great ability in the treatment of SW480 colon cancer cells with a safe, selective and probably a new mode of action.

Published Date: 2020-10-31; Received Date: 2020-10-15