A single serine residue confers tetrodotoxin insensitivity on the rat sensory-neuron-specific sodium channel SNS.
Sensory neurons express a sodium channel (SNS) that is highly resistant to block by tetrodotoxin (IC50 = 60 microM). SNS is 65% homologous to the cardiac sodium channel, in which a single hydrophilic residue in the SS2 segment is critical for tetrodotoxin resistance. By site-directed mutagenesis, we have substituted phenylalanine for serine at the equivalent position in SNS: this mutated (S356F) SNS channel is functionally similar to wild-type SNS when expressed in Xenopus oocytes, but is potently blocked by tetrodotoxin and saxitoxin with IC50s of 2.8 nM and 8.2 nM, respectively. These data provide clues to the rational design of selective blockers of SNS with potential as analgesic drugs.
Sivilotti
L
L
Department of Anatomy, University College London, UK.
Okuse
K
K
Akopian
A N
AN
Moss
S
S
Wood
J N
JN
D000818:Animals; D016297:Mutagenesis, Site-Directed; D062559:NAV1.8 Voltage-Gated Sodium Channel; D009475:Neurons, Afferent / Q000378:metabolism*; D009865:Oocytes; D010649:Phenylalanine / Q000235:genetics; D051381:Rats; D012694:Serine / Q000235:genetics / Q000502:physiology*; D015222:Sodium Channels / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D013779:Tetrodotoxin / Q000378:metabolism / Q000494:pharmacology*; D014981:Xenopus
D062559:NAV1.8 Voltage-Gated Sodium Channel; C568319:Scn10a protein, rat; D015222:Sodium Channels; D013779:Tetrodotoxin; D012694:Serine; D010649:Phenylalanine