Structural Basis for Inhibition of the Voltage-Gated Sodium Channel NaV 1.7 by the Tarantula Toxin HWTX-I

J Biol Chem. 2026 May 8:113130. doi: 10.1016/j.jbc.2026.113130. Online ahead of print.

ABSTRACT

The voltage-gated sodium channel Na_V1.7 is a pivotal therapeutic target for the developing novel, potent, and specific analgesics. HWTX-I, a peptide isolated from the venom of the tarantula Ornithoctonus huwena, is known to inhibit N-type calcium channels and has also been demonstrated to block tetrodotoxin-sensitive (TTX-S) Na_V channels in dorsal root ganglion (DRG) neurons. In this study, we show that HWTX-I potently inhibits Na_V1.7 currents with an IC₅₀ value of 40.6 ± 16.1 nM, but it does not significantly affect the voltage dependence of Na_V1.7 steady-state activation and inactivation. Alanine-scanning mutagenesis revealed that residues K3, V5, F6, P11, N14, E15, W28, and K30 are critical for HWTX-I’s inhibitory activity against Na_V1.7. Furthermore, site-directed mutagenesis analysis demonstrated that HWTX-I binds to the S3-S4 linker in domain II (DII) of Na_V1.7, and the D816K mutation in Na_V1.7 significantly abrogates the efficacy of the HWTX-I-Na_V1.7 interaction. Molecular dynamics (MD) simulations combined with free energy decomposition analysis identified Na_V1.7-D816 and HWTX-I-K3 as dominant energetic contributors to binding, consistent with a role for long-range electrostatic steering rather than a persistent short-range salt bridge. Collectively, these findings elucidate the structural basis of HWTX-I-Na_V1.7 binding, identify the pharmacophore of the toxin, and provide valuable insights into the interactions between peptide toxins and Na_V1.7. Therefore, this research may guide the future development of specific, safe, and efficacious Na_V1.7 inhibitors for pain relief.

PMID:42107643 | DOI:10.1016/j.jbc.2026.113130