Poster Presentation 2014 International Biophysics Congress

Rational engineering defines a molecular switch that is essential for activity of spider-venom peptides against the analgesics target NaV1.7 (#426)

Julie K. Klint 1 , Yanni K. Chin 1 , Glenn F. King 1 2 , Mehdi Mobli 1 2 3
  1. Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
  2. School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
  3. Centre for Advanced Imaging & School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia

The human voltage-gated sodium (hNaV) channel hNaV1.7 is a promising target for the treatment of chronic pain. Many spider toxins modulate the activity of NaV channels and understanding the molecular basis of the toxin-channel interaction is essential for the rational development of venom-based analgesics. Several members of the NaSpTx1 family of spider toxins potently inhibit NaV1.7 (nanomolar IC50)1 . However, one member of this family,µ-TRTX-Hhn2b (Hhn2b), does not inhibit mammalian NaV channels at concentrations up to 100 µM2 . Hhn2b has high sequence identity with other NaSpTx1 members, including amino acid residues that are known to be key determinants for their inhibitory effect, thus providing an interesting opportunity to explore the factors that are essential for the activity of NaSpTx1 toxins.

The three-dimensional structure of Hhn2b was determined using 3D/4D heteronuclear NMR. Data were acquired using nonuniform sampling to speed up data acquisition and improve resolution in the indirect frequency dimensions. Comparison of the high-resolution structure of Hhn2b with other members of the NaSpTx1 family allowed us to rationally engineer this inactive toxin to produce an analog with moderately high potency at hNaV1.7 (IC50 = 440 nM using automated patch clamp electrophysiology). NMR structural studies on the analog revealed a subtle structural change in a b-hairpin motif that we propose is responsible for the gain in potency against hNaV1.7. These findings have allowed us to better define the pharmacophore for this family of peptides, which will facilitate the development of peptide-based analgesics targeted against hNaV1.7.

  1. Klint JK, Senff S, Rupasinghe DB, Er SY, Herzig V, Nicholson GM & King GF (2012) Spider-venom peptides that target voltage-gated sodium channels: pharmacological tools and potential therapeutic leads. Toxicon 60:478-491
  2. Li D, Xiao Y, Hu W, Xie J, Bosmans F, Tytgat J & Liang S (2003) Function and solution structure of hainantoxin-I, a novel insect sodium channel inhibitor from the Chinese bird spider Selenocosmia hainana. FEBS Lett 555:616-622