Identification and targeting of a unique Na _V 1.7 domain driving chronic pain

Abstract

Small molecules directly targeting the voltage-gated sodium channel (VGSC) Na_V1.7 have not been clinically successful. We reported that preventing the addition of a small ubiquitin-like modifier onto the Na_V1.7-interacting cytosolic collapsin response mediator protein 2 (CRMP2) blocked Na_V1.7 function and was antinociceptive in rodent models of neuropathic pain. Here, we discovered a CRMP2 regulatory sequence (CRS) unique to Na_V1.7 that is essential for this regulatory coupling. CRMP2 preferentially bound to the Na_V1.7 CRS over other Na_V isoforms. Substitution of the Na_V1.7 CRS with the homologous domains from the other eight VGSC isoforms decreased Na_V1.7 currents. A cell-penetrant decoy peptide corresponding to the Na_V1.7-CRS reduced Na_V1.7 currents and trafficking, decreased presynaptic Na_V1.7 expression, reduced spinal CGRP release, and reversed nerve injury-induced mechanical allodynia. Importantly, the Na_V1.7-CRS peptide did not produce motor impairment, nor did it alter physiological pain sensation, which is essential for survival. As a proof-of-concept for a Na_V1.7 -targeted gene therapy, we packaged a plasmid encoding the Na_V1.7-CRS in an AAV virus. Treatment with this virus reduced Na_V1.7 function in both rodent and rhesus macaque sensory neurons. This gene therapy reversed and prevented mechanical allodynia in a model of nerve injury and reversed mechanical and cold allodynia in a model of chemotherapy-induced peripheral neuropathy. These findings support the conclusion that the CRS domain is a targetable region for the treatment of chronic neuropathic pain.