Abstract
BPS2025 - Assessing the role of sodium channel fast inactivation in the mechanism of aryl/acyl-sulfonamide inhibition
Biophysical journal, Vol.124(3 Suppl 1), pp.117-118a
02/13/2025
DOI: 10.1016/j.bpj.2024.11.676
Abstract
Regulation of voltage gated sodium channel (VGSC) fast inactivation is critical for electrically excitable tissues, with defects leading to dramatically altered cellular excitability. Aryl/acyl-sulfonamides are next generation VGSC modulators that potently inhibit VGSCs with isoform specificity and are being developed for the treatment of epilepsy and pain. In this study we investigate the NaV1.7 specific arylsulfonamide GX-674 and its dependence on fast inactivation for channel inhibition. GX-674 binds to the activated DIV S4 segment, which is thought to trap the channel in a fast inactivated state. We have generated a NaV1.5/1.7 chimeric channel with NaV1.5 function and expression and NaV1.7 affinity for GX-674. We have assessed the requirement of GX-674 for fast inactivation using NaV1.5/1.7 chimeric channel variants which are deficient in fast inactivation. These constructs further incorporate the C373Y mutation which renders them sensitive to tetrodotoxin (TTX), giving us the ability to probe pore conformation via TTX affinity. NaV1.5/1.7F1586Q (IQM) channels show a 100-fold decrease in GX-674 affinity (IC50: IFM 0.43 nM, IQM 64.87 nM) with a persistent current partially resistant to inhibition. Similar decreases in affinity are seen with “inactivation gate” variants in DIII S6 (I1453A/I1457A: 31.99 nM) and DIV S6 (I1768A/L1772A: 3.05 nM), but these channels can be fully inhibited. The non-inactivating D1S6 L409C/A410W (CW) mutant retains GX-674 affinity but cannot be fully inhibited. However, this GX-resistant current displays decreased TTX sensitivity, suggesting coupling between GX inhibition and the selectivity filter. These findings show that GX-674 requires fast inactivation for efficacious channel inhibition, however additional mechanisms may be required to explain the observed inhibition of non-fast inactivating currents. Further studies will assess this possibility by analyzing single channel conductance and probing selectivity filter conformation with pore blocking agents.
Details
- Title: Subtitle
- BPS2025 - Assessing the role of sodium channel fast inactivation in the mechanism of aryl/acyl-sulfonamide inhibition
- Creators
- Samantha G. ThompsonColin ClarkLionel GissotJason D. GalpinDaniel T. InfieldChristopher A. Ahern
- Resource Type
- Abstract
- Publication Details
- Biophysical journal, Vol.124(3 Suppl 1), pp.117-118a
- DOI
- 10.1016/j.bpj.2024.11.676
- ISSN
- 0006-3495
- Language
- English
- Date published
- 02/13/2025
- Academic Unit
- Molecular Physiology and Biophysics; Iowa Neuroscience Institute
- Record Identifier
- 9984790995402771
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