Computational design of peptides stabilizing Nav1.7 channel in an inactivated state.

Abstract

Chronic pain affects about 20% of the US population and safe treatments for chronic pain are extremely limited. Developing effective and safe therapeutics to treat chronic pain remains an unmet medical need. Voltage-gated sodium (Nav) channel Nav1.7 has been identified as one of the key players in the pain signaling pathway and, therefore, is considered a promising molecular target to develop novel non-addictive therapeutic approaches to treating chronic pain. Nevertheless, achieving high subtype selectivity when targeting Nav channels is of primary importance to avoid impairing vital physiological functions mediated by off-target channels. Efforts to selectively target Nav1.7 have been hindered by the difficulties in targeting Nav1.7 over other Nav channel subtypes. Peptidic gating modifier toxins (GMTs), such as Protoxin-II (ProTx2), are promising scaffolds for novel peptide design targeting ion channels with high potency and subtype selectivity. ProTx2 binds to the second and fourth voltage-sensing domains (VSDII & VSDIV) from Nav1.7 with large subtype selectivity and can modulate both channel activation and inactivation. In this project, we modeled ProTx2 bound to the activated-VSDIV of the experimental structure of human Nav1.7. Subsequently, we used protein design to generate ProTx2 variants with increased predicted binding affinity for activated-VSDIV from NaV1.7. We anticipate that trapping the VSDIV in an activated conformation will stabilize an inactivated state of the channel. Designs that result in Nav1.7 inactivation with large potency and subtype selectivity will be promising candidates to define a new class of biologics to treat chronic pain.