Enzymatic Ligation of a Pore Blocker Toxin and a Gating Modifier Toxin: Creating Double-Knotted Peptides with Improved Sodium Channel Na1.7 Inhibition.

Disulfide-rich animal venom peptides targeting either the voltage-sensing domain or the pore domain of voltage-gated sodium channel 1.7 (Na1.7) have been widely studied as drug leads and pharmacological probes for the treatment of chronic pain. However, despite intensive research efforts, the full potential of Na1.7 as a therapeutic target is yet to be realized. In this study, using evolved sortase A, we enzymatically ligated two known Na1.7 inhibitors-PaurTx3, a spider-derived peptide toxin that modifies the gating mechanism of the channel through interaction with the voltage-sensing domain, and KIIIA, a small cone snail-derived peptide inhibitor of the pore domain-with the aim of creating a bivalent inhibitor which could interact simultaneously with two noncompeting binding sites. Using electrophysiology, we determined the activity at Na1.7, and to maximize potency, we systematically evaluated the optimal linker length, which was nine amino acids. Our optimized synthetic bivalent peptide showed improved channel affinity and potency at Na1.7 compared to either PaurTx3 or KIIIA individually. This work shows that novel and improved Na1.7 inhibitors can be designed by combining a pore blocker toxin and a gating modifier toxin to confer desired pharmacological properties from both the voltage sensing domain and the pore domain.