GPR35 modulates Na_V1.9 gating and sensory neuron excitability

The voltage-gated Na⁺ channel Na_V1.9 is a determinant of excitability in sensory neurons, yet the upstream G-protein-coupled receptors (GPCRs) that regulate its activity remain poorly defined. Here, we identify GPR35 as a modulator of Na_V1.9 function in dorsal root ganglion (DRG) neurons, establishing a previously unrecognized receptor-channel signalling axis.

Transcriptomics of Na_V1.9-expressing neurons, proximity ligation assays, patch-clamp electrophysiology in primary mouse DRG neurons and a genetic mouse model were combined to assess spatial and functional relationships between GPR35 and Na_V1.9. Pharmacological activation of GPR35 was examined using cromolyn disodium, whereas zaprinast and sildenafil were used to probe potential cGMP-dependent mechanisms.

GPR35 transcripts were enriched in Na_V1.9-positive neurons and proximity assays demonstrated spatial association between both proteins in DRG neurons. Activation of GPR35 with cromolyn disodium potentiated Na_V1.9 currents, accelerated channel gating and modified neuronal excitability, reflected by increased action potential overshoot and upstroke velocity. These effects were absent from GPR35-deficient DRG neurons. Zaprinast and the phosphodiesterase-5 inhibitor sildenafil also potentiated Na_V1.9 currents in a GPR35-dependent manner, indicating that cGMP-associated signalling requires GPR35 expression to influence Na_V1.9. Under inflammatory conditions induced by prostaglandin E₂, GPR35 activation partially attenuated Na_V1.9 potentiation but did not restore normal excitability.

These findings identify GPR35 as a regulator of Na_V1.9 and define a receptor-channel signalling module linking GPCR activation to ion channel-dependent modulation of sensory neuron excitability. This work provides a mechanistic framework for understanding GPCR-Na_V1.9 coupling.