Modulation of hNav by Tst1, a β-toxin purified from the scorpion Tityus stigmurus.

Scorpion venoms are known as a rich mixture of components, including peptides that can interact with different ion channels, particularly voltage-gated potassium channels (Kv), calcium channels (Cav) and sodium channels (Nav), essential membrane proteins for various physiological functions in organisms. The present work aimed to characterize the modulation of hNa-channels by Tst1, a peptide purified from the venom of Tityus stigmurus, using whole-cell patch clamp. Tst1 at 100 nM provoked current inhibition in Nav 1.3 (85.23%), Nav 1.2 (67.26%) and Nav 1.4 (63.43%), while Nav 1.1, 1.5, 1.6, and 1.7 were not significantly affected. Tst1 also shifted the voltage of activation and steady-state inactivation to more hyperpolarized states and altered the recovery from inactivation of the channels, reducing repetitive firing of cells, which was more effective in Nav 1.3. Tst1 also demonstrated that the effect on Nav 1.3 is dose-dependent, with an IC50 of 8.79 nM. Taken together, these results confirmed that Tst1, the first Tityus stigmurus NaScTx assayed in relation to Nav channels, is a β-toxin, as was previously suggested due to its amino acid sequence. KEY CONTRIBUTION: First β-toxin purified from the venom of Tityus stigmurus scorpion broadly characterized in hNa+-channels.