TsAP-1

Here we report two novel 17-mer amidated linear peptides (TsAP-1 and TsAP-2) whose structures were deduced from cDNAs cloned from a venom-derived cDNA library of the Brazilian yellow scorpion, Tityus serrulatus. Both mature peptides were structurally-characterised following their location in chromatographic fractions of venom and synthetic replicates of each were subjected to a range of biological assays. The peptides were each active against model test micro-organisms but with different potencies. TsAP-1 was of low potency against all three test organisms (MICs 120-160 μM), whereas TsAP-2 was of high potency against the Gram-positive bacterium, Staphylococcus aureus (MIC 5 μM) and the yeast, Candida albicans (10 μM). Haemolytic activity of TsAP-1 was low (4% at 160 μM) and in contrast, that of TsAP-2 was considerably higher (18% at 20 μM). Substitution of four neutral amino acid residues with Lys residues in each peptide had dramatic effects on their antimicrobial potencies and haemolytic activities, particularly those of TsAP-1. The MICs of the enhanced cationic analogue (TsAP-S1) were 2.5 μM for S. aureus/C. albicans and 5 μM for E. coli but with an associated large increase in haemolytic activity (30% at 5 μM). The same Lys residue substitutions in TsAP-2 produced a dramatic effect on its MIC for E. coli lowering this from >320 μM to 5 μM. TsAP-1 was ineffective against three of the five human cancer cell lines tested while TsAP-2 inhibited the growth of all five. Lys residue substitution of both peptides enhanced their potency against all five cell lines with TsAp-S2 being the most potent with IC50 values ranging between 0.83 and 2.0 μM. TsAP-1 and TsAP-2 are novel scorpion venom peptides with broad spectrum antimicrobial and anticancer cell activities the potencies of which can be significantly enhanced by increasing their cationicity.

Host defense peptides (HDPs) are a class of evolutionarily conserved substances of the innate immune response that have been identified as major players in the defense system in many living organisms. Some of the HDPs are also referred to as peptidotoxins, which offer immense potential for anticancer therapy. However, their therapeutic potential is yet to be fully translated mainly due to their off-target toxicity. Here we show that their nanoenabled delivery may become beneficial in controlling their delivery in intracellular space. We introduced an amphiphilic polymer to synthesize a well-defined, self-assembled, rigid-cored polymeric nanoarchitecture for controlled delivery of three model peptidotoxins, i.e., melittin, TSAP-1, and a negative control peptide of synthetic origin. Interestingly, our results revealed strong interaction of peptidotoxins with duplex plasmid DNA. Extensive biophysical characterization (UV-vis spectroscopy, gel electrophoresis, MTT assay, and flow assisted cell sorting) experimentally verified that peptidotoxins were able to interact with genomic DNA in vitro and in turn influence the cancer cell growth. Thus, we unraveled that, through genomic DNA regulation, peptidotoxins can play a role in cell cycle regulation and exert their anticancer activities.