Purification and electrophysiological characterization of the Tf4 peptide isolated from the scorpion Tityus fasciolatus on the voltage-gated sodium channel Nav1.2

In the animal kingdom, arthropods of the class Arachnida, such as spiders and scorpions, are the main contributors to most human incidents caused by animals worldwide. Species in the Buthidae family, such as Tityus fasciolatus, are important for the study and characterization of scorpion toxins. 

The venom of these animals comprises a diverse array of bioactive components, with peptides being the key elements responsible for the symptoms most commonly observed in scorpion sting incidents. These peptides can be classified as NDBPs (non-disulfide bond peptides) and DBPs (disulfide bond peptides). DBP-type peptides are regarded as the primary agents of the neurotoxic activity in scorpion venom, especially those that modulate Na+ and K+ channels.

Sodium channels are transmembrane proteins that form a pore allowing the passage of sodium ions, and they are found in excitable cells, such as muscles and neurons. They play a crucial role in membrane potential changes near the threshold for firing, initiation and propagation of action potentials, and the generation of pre and post synaptic graded potentials.

The aim of this study was to observe the electrophysiological activity of the peptide Tf4, purified from the venom of the scorpion Tityus fasciolatus, in HEK cells expressing Nav1.2 channels. The peptide was purified using reverse-phase high-performance liquid chromatography (RP-HPLC), and electrophysiological assays were conducted using the Patch Clamp technique, applying activation, inactivation, and recovery protocols. At a concentration of 1 μM in Nav1.2 channels, the Tf4 toxin inhibited currents by 7.15 ± 2.08%. The ΔV1/2 activation values were -3.13 ± 1.50 mV, and the ΔV1/2 inactivation values were -1.49 ± 0.75 mV.

Tf4 is the most abundant toxin found in the venom of T. fasciolatus. It is currently classified as an α-NaScTx (alpha-scorpion sodium channel toxin) and shares a high percentage of identity with other scorpion toxins from the genus Tityus, such as TcoNTxP1 and TbIT-1, classified as insect-like. Its similarity to these toxins suggests that Tf4 may act on Nav channels in insects. Future studies will include electrophysiological assays on different subtypes of voltage-dependent sodium channels to better understand Tf4's activity.