Explore the vast range of titles available.

The structure-function and optimization studies of Na V -inhibiting spider toxins have focused on developing selective inhibitors for peripheral pain-sensing Na V 1.7. With several Na V subtypes emerging as potential therapeutic targets, structure-function analysis of Na V -inhibiting spider toxins at such subtypes is warranted. Using the recently discovered spider toxin Ssp1a, this study extends the structure-function relationships of Na V -inhibiting spider toxins beyond Na V 1.7 to include the epilepsy target Na V 1.2 and the pain target Na V 1.3. Based on these results and docking studies, we designed analogues for improved potency and/or subtype-selectivity, with S7R-E18K-rSsp1a and N14D-P27R-rSsp1a identified as promising leads. S7R-E18K-rSsp1a increased the rSsp1a potency at these three Na V subtypes, especially at Na V 1.3 (∼10-fold), while N14D-P27R-rSsp1a enhanced Na V 1.2/1.7 selectivity over Na V 1.3. This study highlights the challenge of developing subtype-selective spider toxin inhibitors across multiple Na V subtypes that might offer a more effective therapeutic approach. The findings of this study provide a basis for further rational design of Ssp1a and related NaSpTx1 homologs targeting Na V 1.2, Na V 1.3 and/or Na V 1.7 as research tools and therapeutic leads.

Given the important role of voltage-gated sodium (Na V ) channel-modulating spider toxins in elucidating the function, pharmacology, and mechanism of action of therapeutically relevant Na V channels, we screened the venom from Australian theraphosid species against the human pain target hNa V 1.7. Using assay-guided fractionation, we isolated a 33-residue inhibitor cystine knot (ICK) peptide (Ssp1a) belonging to the NaSpTx1 family. Recombinant Ssp1a (rSsp1a) inhibited neuronal hNa V subtypes with a rank order of potency hNa V 1.7 > 1.6 > 1.2 > 1.3 > 1.1. rSsp1a inhibited hNa V 1.7, hNa V 1.2 and hNa V 1.3 without significantly altering the voltage-dependence of activation, inactivation, or delay in recovery from inactivation. However, rSsp1a demonstrated voltage-dependent inhibition at hNa V 1.7 and rSsp1a-bound hNa V 1.7 opened at extreme depolarizations, suggesting rSsp1a likely interacted with voltage-sensing domain II (VSD II) of hNa V 1.7 to trap the channel in its resting state. Nuclear magnetic resonance spectroscopy revealed key structural features of Ssp1a, including an amphipathic surface with hydrophobic and charged patches shown by docking studies to comprise the interacting surface. This study provides the basis for future structure-function studies to guide the development of subtype selective inhibitors.