Key Points
- Identify the binding mechanism and structural determinants governing subtype-selective small molecule inhibition of voltage-gated sodium channels away from the central pore.
- Characterized the inhibitory activity and selectivity of two nanomolar-potent small molecules (ICA-121431 and PF-04856264) against human Nav isoforms (Nav1.1–Nav1.7).
- Mapped binding interactions using chimeric sodium channels and single point mutations within the Domain 4 voltage sensor segment.
- ICA-121431 inhibited Nav1.3/Nav1.1 with an IC50 of 19 nM, and PF-04856264 inhibited Nav1.7 with an IC50 of 28 nM, showing up to 1,000-fold selectivity against other isoforms, including Nav1.5.
- Selectivity mapped to extracellular-facing regions of the S2 and S3 transmembrane segments within the Domain 4 S1–S4 voltage sensor, distinct from pore and local anesthetic sites.
- Identified critical determinants including residues E1559 in Nav1.3 and D1586 in Nav1.7, which overlap with polypeptide toxin Site 3.
Structured PICO
PPopulationVoltage-gated sodium (Nav) channels (human Nav1.3/Nav1.1 and Nav1.7) using chimeras and single point mutations
IInterventionSmall molecule Nav channel inhibitors (ICA-121431 and PF-04856264)
OOutcomeInteraction site on the sodium channel and determinants of subtype selectivity
Identifies a unique interaction site on the Domain 4 voltage sensor segment for subtype-selective small molecule sodium channel inhibitors, distinct from the pore region.