Rational engineering defines a molecular switch that is essential for activity of spider-venom peptides against the analgesics target Na<sub>V</sub>1.7 — ASN Events
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  2. Session Seven - Poster Session B Including Happy Hour & Trade Display
  3. Rational engineering defines a molecular switch that is essential for activity of spider-venom peptides against the analgesics target NaV1.7

Rational engineering defines a molecular switch that is essential for activity of spider-venom peptides against the analgesics target NaV1.7 (#229)

Yanni KY Chin 1 , Julie Klint 1 , Mehdi Mobli 1 2
  1. Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, Australia
  2. Centre of Advanced Imaging, University of Queensland, St Lucia, 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 show great potential as leads for development of analgesics. Understanding the molecular basis of the toxin-channel interaction is essential for the rational development of target-specific venom-based analgesics. Several members of the NaSpTx1 family of spider toxins potently inhibit NaV1.7 (nanomolar IC50)1. However, one member of the family, µ–TRTX–Hhn2b (Hhn2b), does not inhibit mammalian NaV1.7 at concentrations of up to 100 μM2, despite its high sequence identity with other NaSpTx1 members. Investigation of the differences between the inactive Hhn2b and the closely related active toxins in this family could therefore identify key molecular features that govern the inhibitory activities of spider toxins on NaV channels.

Comparison of the sequences of Hhn2b and several hNav1.7-modulating toxins guided us to rationally engineer this inactive toxin to produce analogs with moderately high potency at hNav1.7. Besides the gain in potency against hNav1.7, liposome-binding studies using NMR have also shown that the active Hhn2b analogs are more susceptible to lipid binding, reflecting that lipid interactions might be a prerequisite for these toxins to bind to the membrane-embedded ion channels.

The three-dimensional structures of Hhn2b and an active analog were 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. Structural studies on the toxins revealed a subtle structural difference in a b-hairpin motif as well as a change in a hydrophobic patch. We propose that they are responsible for the differences we observed in the potency against hNav1.7 and the affinity for lipids. These findings have allowed us to better define the pharmacophore for this class 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