Computational Design of High-Affinity Blockers for Sodium Channel NaV 1.2 from µ-Conotoxin KIIIA

Abstract

The voltage-gated sodium channel subtype 1.2 (NaV 1.2) is instrumental in the initiation of action potentials in the nervous system, making it a natural drug target for neurological diseases. Therefore, there is much pharmacological interest in finding blockers of NaV 1.2 and improving their affinity and selectivity properties. An extensive family of peptide toxins from cone snails (conotoxins) block NaV channels, thus they provide natural templates for the design of drugs targeting NaV channels. Unfortunately, progress was hampered due to the absence of any NaV structures. The recent determination of cryo-EM structures for NaV channels has finally broken this impasse. Here, we use the NaV 1.2 structure in complex with µ-conotoxin KIIIA (KIIIA) in computational studies with the aim of improving KIIIA’s affinity and blocking capacity for NaV 1.2. Only three KIIIA amino acid residues are available for mutation (S5, S6, and S13). After performing molecular modeling and simulations on NaV 1.2–KIIIA complex, we have identified the S5R, S6D, and S13K mutations as the most promising for additional contacts. We estimate these contacts to boost the affinity of KIIIA for NaV 1.2 from nanomole to picomole domain. Moreover, the KIIIA[S5R, S6D, S13K] analogue makes contacts with all four channel domains, thus enabling the complete blocking of the channel (KIIIA partially blocks as it has contacts with three domains). The proposed KIIIA analogue, once confirmed experimentally, may lead to novel anti-epileptic drugs.