A C-Terminal Fragment of Chlorotoxin Retains Bioactivity and Inhibits Cell Migration

Abstract

Chlorotoxin was originally isolated from the venom of the Israeli scorpion Leiurus quinquestriatus, and has potential as a tumor imaging agent based on its selective binding to tumor cells. Several targets have been suggested for chlorotoxin including voltage-gated chloride channels, and it has been shown to have anti-angiogenic activity and inhibit cell migration. The structure of chlorotoxin is stabilized by four disulfide bonds and contains β-sheet and helical structure. Interestingly, the reduced form has previously been shown to inhibit cell migration to the same extent as the wild type, but structural analysis indicates that the reduced form of the peptide does not maintain the native secondary structure and appears unstructured in solution. This lack of structure suggests that a short stretch of amino acids might be responsible for the bioactivity. To explore this hypothesis, we have synthesized fragments of chlorotoxin without disulfide bonds. As expected for such small peptides, NMR analysis indicated that the peptides were unstructured in solution. However, the peptide corresponding to the eight C-terminal residues inhibited cell migration, in contrast to the other fragments. Our results suggest that the C-terminal region plays a critical role in the bioactivity of chlorotoxin.

Recombinantly expressed MeICT, a new toxin from Mesobuthus eupeus scorpion, inhibits glioma cell proliferation and downregulates Annexin A2 and FOXM1 genes

“…On the other hand, Othman et al showed that residues 29-36 (8 C-ter residues) of CTX directly interact with MMP-2 (Othman et al, 2017). Furthermore, a recent study indicated that eight C-terminal residues of CTX are fundamental for its bioactivity and inhibition of cell migration (Dastpeyman et al, 2019). Seven C-ter residues of CTX and MeICT are identical and only Y 29 in CTX has been replaced with F 29 in MeICT, that both are aromatic residues with similar biochemical properties.…”

Modifications of Plasma Membrane Organization in Cancer Cells for Targeted Therapy

“…The endocytosis of the complexes induced via binding of CTX contributes to chloride ion efflux in cells [114,115]. Synthetic chlorotoxin derivatives were used successfully in both preclinical and clinical trials of glioma therapies [116][117][118]. Potassium transporters play a crucial role in cell membrane potential.…”

Targeting tumor resistance mechanisms

“…It is being evaluated as a new diagnostic drug in a phase II/III clinical trial to determine how well the drug can help distinguish between tumor and normal tissue during surgery in pediatric primary central nervous system tumors (NCT03579602). What is unique with this peptide is that it is retained in the tumor and can cross the blood–brain barrier 96 . Chlorotoxin molecular targets include the CLC-3 voltage-gated chloride channel, annexin-2, and matrix metalloproteinase-2 96 – 99 .…”

“…What is unique with this peptide is that it is retained in the tumor and can cross the blood–brain barrier 96 . Chlorotoxin molecular targets include the CLC-3 voltage-gated chloride channel, annexin-2, and matrix metalloproteinase-2 96 – 99 . SOR-C13 is a carboxy-terminal truncation of soricidin, a 54-residue paralytic peptide found in the venom of the short-tailed shrew Blarina brevicauda .…”