Identification and Characterization of Voltage-Gated Potassium Channels as the Cell Surface Target that Mediates the Anti-Proliferative Activity of Snake Venom Myotoxins

Abstract

Background: Myotoxins are a family of small protein toxins present in the venom of multiple species of pit vipers that have selective toxic effects on different types of tissues. Method: In order to better protect people from these toxins and to potentially develop these proteins as the basis for new therapeutics, we investigated the mechanism of the cytotoxicity of a specific myotoxin, helleried crotamine (HR-crotamine). Results: The results we have obtained demonstrate the specific and selective binding of HRcrotamine to selected voltage gated potassium (Kv) channels (Kv1.1, Kv1.2, Kv1.3). The expression level of these channel proteins correlates positively with the effect of HRcrotamine on the inhibition of proliferation in multiple cancer cell lines. The binding of HR-crotamine to Kv1.3 in Jurkat cells is associated with the inhibition of intracellular calcium influx as reflected by the inhibition of NFAT translocation and the inhibition of IL-2 secretion. Discussion: These results indicate a direct connection between the binding of HR-crotamine to cell surface Kv1.3 channel and the inhibition of cell proliferation mediated by the suppression of intracellular Ca2+ signaling. Conclusion: We have characterized the cell surface-binding target for HR-crotamine that mediates its effects on intracellular signaling. In future studies, the mechanistic model we have developed can be used to develop single-chain antibody molecules (scFv proteins) that can be used both as molecular probes and HR-crotamine anti-toxins. These antibodies may be used to decrease the myotoxin toxicity, which is an important component in the pathophysiology of rattlesnake snakebite.