Electrophysiological properties of mutant Nav1.7 sodium channels in a painful inherited neuropathy.
Although the physiological basis of erythermalgia, an autosomal dominant painful neuropathy characterized by redness of the skin and intermittent burning sensation of extremities, is not known, two mutations of Na(v)1.7, a sodium channel that produces a tetrodotoxin-sensitive, fast-inactivating current that is preferentially expressed in dorsal root ganglia (DRG) and sympathetic ganglia neurons, have recently been identified in patients with primary erythermalgia. Na(v)1.7 is preferentially expressed in small-diameter DRG neurons, most of which are nociceptors, and is characterized by slow recovery from inactivation and by slow closed-state inactivation that results in relatively large responses to small, subthreshold depolarizations. Here we show that these mutations in Na(v)1.7 produce a hyperpolarizing shift in activation and slow deactivation. We also show that these mutations cause an increase in amplitude of the current produced by Na(v)1.7 in response to slow, small depolarizations. These observations provide the first demonstration of altered sodium channel function associated with an inherited painful neuropathy and suggest that these physiological changes, which confer hyperexcitability on peripheral sensory and sympathetic neurons, contribute to symptom production in hereditary erythermalgia.
Cummins
Theodore R
TR
Department of Pharmacology and Toxicology, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
Dib-Hajj
Sulayman D
SD
Waxman
Stephen G
SG
D019943:Amino Acid Substitution; D002460:Cell Line; D004594:Electrophysiology; D004916:Erythromelalgia / Q000235:genetics*; D005799:Genes, Dominant; D006801:Humans; D009154:Mutation / Q000235:genetics*; D062556:NAV1.7 Voltage-Gated Sodium Channel; D009437:Neuralgia / Q000235:genetics*; D018408:Patch-Clamp Techniques; D015222:Sodium Channels / Q000235:genetics* / Q000378:metabolism*; D014162:Transfection
D062556:NAV1.7 Voltage-Gated Sodium Channel; C486866:SCN9A protein, human; D015222:Sodium Channels