Profiling endogenous sodium channels in the ND7-23 neuroblastoma cell line: implications for use as a heterologous ion channel expression system and native tissue model suitable for automated patch-clamp screening

Voltage-dependent sodium channels (Na_v) are implicated in a wide range of diseases, with their role in triggering and modulating membrane excitability making them key drug discovery targets for cardiac and neurological indications. Neuronal Na_v’s are divided into TTX-sensitive (Na_v1.1, Na_v1.2, Na_v1.3, Na_v1.6 and Na_v1.7) and TTX-resistant channels (Na_v1.8 and Na_v1.9), with those found in the CNS underlying various types of epilepsy and those expressed in the periphery implicated in many types of pain behaviour such as inflammatory, neuropathic, chemotherapy and cancer-induced pain, as well as visceral pain conditions such as irritable bowel syndrome (IBS). Key to the role of Na_vs in pain is their specific distribution and function in peripheral sensory nociceptors of the dorsal root (DRG) and other sensory ganglia, where Na_v1.x channel function changes after injury through the effects of inflammatory mediators and signalling pathways, and channels are redistributed from the soma to axons.² In this way Na_v activity increases neuronal excitability and induces spontaneous, persistent, repetitive and ectopic action potential firing. The role of peripheral Na_vs in pain are supported by the association of SNPs and genetic mutations in Na_v1.7 with several pain several phenotypes (CIP, PEPD and IEM)³ and gain-of-function mutations in Na_v1.7 and Na_v1.8 in human patients suffering from small fibre neuropathy (SFN).