title: Analysis of the structural and molecular basis of voltage-sensitive sodium channel inhibition by the spider toxin huwentoxin-IV (μ-TRTX-Hh2a).
abstract: Voltage-gated sodium channels (VGSCs) are essential to the normal function of the vertebrate nervous system. Aberrant function of VGSCs underlies a variety of disorders, including epilepsy, arrhythmia, and pain. A large number of animal toxins target these ion channels and may have significant therapeutic potential. Most of these toxins, however, have not been characterized in detail. Here, by combining patch clamp electrophysiology and radioligand binding studies with peptide mutagenesis, NMR structure determination, and molecular modeling, we have revealed key molecular determinants of the interaction between the tarantula toxin huwentoxin-IV and two VGSC isoforms, Nav1.7 and Nav1.2. Nine huwentoxin-IV residues (F6A, P11A, D14A, L22A, S25A, W30A, K32A, Y33A, and I35A) were important for block of Nav1.7 and Nav1.2. Importantly, molecular dynamics simulations and NMR studies indicated that folding was normal for several key mutants, suggesting that these amino acids probably make specific interactions with sodium channel residues. Additionally, we identified several amino acids (F6A, K18A, R26A, and K27A) that are involved in isoform-specific VGSC interactions. Our structural and functional data were used to model the docking of huwentoxin-IV into the domain II voltage sensor of Nav1.7. The model predicts that a hydrophobic patch composed of Trp-30 and Phe-6, along with the basic Lys-32 residue, docks into a groove formed by the Nav1.7 S1-S2 and S3-S4 loops. These results provide new insight into the structural and molecular basis of sodium channel block by huwentoxin-IV and may provide a basis for the rational design of toxin-based peptides with improved VGSC potency and/or selectivity.
authors.affiliation: Department of Neuroscience Discovery, Janssen Research & Development, LLC, San Diego, California 92121, USA.
authors.forename: Natali A
authors.initials: NA
authors.lastname: Minassian
authors.forename: Alan
authors.initials: A
authors.lastname: Gibbs
authors.forename: Amy Y
authors.initials: AY
authors.lastname: Shih
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.forename: Robert A
authors.initials: RA
authors.lastname: Neff
authors.forename: Steven W
authors.initials: SW
authors.lastname: Sutton
authors.forename: Tara
authors.initials: T
authors.lastname: Mirzadegan
authors.forename: Judith
authors.initials: J
authors.lastname: Connor
authors.forename: Ross
authors.initials: R
authors.lastname: Fellows
authors.forename: Matthew
authors.initials: M
authors.lastname: Husovsky
authors.forename: Serena
authors.initials: S
authors.lastname: Nelson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hunter
authors.forename: Mack
authors.initials: M
authors.lastname: Flinspach
authors.forename: Alan D
authors.initials: AD
authors.lastname: Wickenden
mesh_terms: D000595:Amino Acid Sequence; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating; D009682:Magnetic Resonance Spectroscopy; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011869:Radioligand Assay; D017386:Sequence Homology, Amino Acid; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D013111:Spider Venoms / Q000737:chemistry* / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D026941:Sodium Channel Blockers; D013111:Spider Venoms; C470632:huwentoxin IV, Selenocosmia huwena
keywords: Electrophysiology; Ion Channels; Sodium Channels; Structural Biology; Toxins