title: Erythromelalgia mutation Q875E Stabilizes the activated state of sodium channel Nav1.7.
abstract: The human voltage-gated sodium channel Nav1.7 plays a crucial role in transmission of noxious stimuli. The inherited pain disorder erythromelalgia (IEM) has been linked to Nav1.7 gain-of-function mutations. Here we show that the IEM-associated Q875E mutation located on the pore module of Nav1.7 produces a large hyperpolarizing shift (-18 mV) in the voltage dependence of activation. Three-dimensional homology modeling indicates that the side chains of Gln-875 and the gating charge Arg-214 of the domain I voltage sensor are spatially close in the activated conformation of the channel. We verified this proximity by using an engineered disulfide bridge approach. The Q875E mutation introduces a negative charge that may modify the local electrical field experienced by the voltage sensor and, upon activation, interact directly via a salt bridge with the Arg-214 gating charge residue. Together these processes could promote transition to, and stabilization of, the domain I voltage sensor in the activated conformation and thus produce the observed gain of function. In support of this hypothesis, an increase in the extracellular concentration of Ca(2+) or Mg(2+) reverted the voltage dependence of activation of the IEM mutant to near WT values, suggesting a cation-mediated electrostatic screening of the proposed interaction between Q875E and Arg-214.
authors.affiliation: From the Institute of Physiology and Pathophysiology, Friedrich-Alexander Universität Erlangen-Nürnberg, 91054 Erlangen, Germany.
authors.forename: Theresa
authors.initials: T
authors.lastname: Stadler
authors.affiliation: From the Institute of Physiology and Pathophysiology, Friedrich-Alexander Universität Erlangen-Nürnberg, 91054 Erlangen, Germany, the School of Natural Sciences and Psychology, Liverpool John Moores University, Liverpool, Merseyside L3 3AF, United Kingdom, and.
authors.forename: Andrias O
authors.initials: AO
authors.lastname: O'Reilly
authors.affiliation: From the Institute of Physiology and Pathophysiology, Friedrich-Alexander Universität Erlangen-Nürnberg, 91054 Erlangen, Germany, the Institute of Physiology, RWTH Aachen University Hospital, 52074 Aachen, Germany alampert@ukaachen.de.
authors.forename: Angelika
authors.initials: A
authors.lastname: Lampert
mesh_terms: D002118:Calcium / Q000378:metabolism; D004916:Erythromelalgia / Q000235:genetics* / Q000473:pathology; D057809:HEK293 Cells; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D062556:NAV1.7 Voltage-Gated Sodium Channel / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010146:Pain / Q000235:genetics* / Q000473:pathology; D018408:Patch-Clamp Techniques; D015222:Sodium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D062556:NAV1.7 Voltage-Gated Sodium Channel; C486866:SCN9A protein, human; D015222:Sodium Channels; D008274:Magnesium; D002118:Calcium
keywords: Disulfide Locking; Electrophysiology; Molecular Modeling; Neurophysiology; Pain; Patch Clamp