Characterization of the coupling mechanism of scorpion ß-neurotoxins on the voltage-gated sodium channel hNav1.6.

Scorpion ß-neurotoxins represent a pharmacological group that affects voltage-gated sodium channels (Nav). Despite knowing the electrophysiological effect of these toxins on Nav channels, the molecular mechanism by which the union is carried out is still undetermined. In this study, computational techniques such as modeling, docking and molecular dynamics were used to elucidate the mechanism of interaction between scorpion ß-neurotoxins using the neurotoxin nCssII and its recombinant variant CssII-RCR, which bind to the site-4, an extracellular receptor, of the human sodium channel hNav1.6. Different modes of interaction were observed for both toxins, where the main distinguishing feature was the interaction generated by the residue E15 on such site-4; that is, E15 in nCssII exhibits an interaction with the voltage-sensing domain II, and the same residue E15 of CssII-RCR exhibits an interaction with domain III. Despite this difference in interaction by E15, it is seen that both neurotoxins interact with similar regions of the voltage sensing domain such as the S3-S4 connecting loop (L834-E838) of the hNav1.6. Our simulations present a first approach to the mode of interaction of scorpion beta-neurotoxins in toxin-receptor complexes, being able to explain at the molecular level the phenomenon of voltage sensor entrapment generated by these toxins.Communicated by Ramaswamy H. Sarma.

A Novel Insecticidal Spider Peptide that Affects the Mammalian Voltage-Gated Ion Channel hKv1.5.

Spider venoms include various peptide toxins that modify the ion currents, mainly of excitable insect cells. Consequently, scientific research on spider venoms has revealed a broad range of peptide toxins with different pharmacological properties, even for mammal species. In this work, thirty animal venoms were screened against hKv1.5, a potential target for atrial fibrillation therapy. The whole venom of the spider Oculicosa supermirabilis, which is also insecticidal to house crickets, caused voltage-gated potassium ion channel modulation in hKv1.5. Therefore, a peptide from the spider O. supermirabilis venom, named Osu1, was identified through HPLC reverse-phase fractionation. Osu1 displayed similar biological properties as the whole venom; so, the primary sequence of Osu1 was elucidated by both of N-terminal degradation and endoproteolytic cleavage. Based on its primary structure, a gene that codifies for Osu1 was constructed de novo from protein to DNA by reverse translation. A recombinant Osu1 was expressed using a pQE30 vector inside the E. coli SHuffle expression system. recombinant Osu1 had voltage-gated potassium ion channel modulation of human hKv1.5, and it was also as insecticidal as the native toxin. Due to its novel primary structure, and hypothesized disulfide pairing motif, Osu1 may represent a new family of spider toxins.