title: Structure and function of hainantoxin-III, a selective antagonist of neuronal tetrodotoxin-sensitive voltage-gated sodium channels isolated from the Chinese bird spider Ornithoctonus hainana.
abstract: In the present study, we investigated the structure and function of hainantoxin-III (HNTX-III), a 33-residue polypeptide from the venom of the spider Ornithoctonus hainana. It is a selective antagonist of neuronal tetrodotoxin-sensitive voltage-gated sodium channels. HNTX-III suppressed Nav1.7 current amplitude without significantly altering the activation, inactivation, and repriming kinetics. Short extreme depolarizations partially activated the toxin-bound channel, indicating voltage-dependent inhibition of HNTX-III. HNTX-III increased the deactivation of the Nav1.7 current after extreme depolarizations. The HNTX-III·Nav1.7 complex was gradually dissociated upon prolonged strong depolarizations in a voltage-dependent manner, and the unbound toxin rebound to Nav1.7 after a long repolarization. Moreover, analysis of chimeric channels showed that the DIIS3-S4 linker was critical for HNTX-III binding to Nav1.7. These data are consistent with HNTX-III interacting with Nav1.7 site 4 and trapping the domain II voltage sensor in the closed state. The solution structure of HNTX-III was determined by two-dimensional NMR and shown to possess an inhibitor cystine knot motif. Structural analysis indicated that certain basic, hydrophobic, and aromatic residues mainly localized in the C terminus may constitute an amphiphilic surface potentially involved in HNTX-III binding to Nav1.7. Taken together, our results show that HNTX-III is distinct from β-scorpion toxins and other β-spider toxins in its mechanism of action and binding specificity and affinity. The present findings contribute to our understanding of the mechanism of toxin-sodium channel interaction and provide a useful tool for the investigation of the structure and function of sodium channel isoforms and for the development of analgesics.
authors.affiliation: College of Life Sciences, Hunan Normal University, Changsha, Hunan, 410081, China. liuzh@hunnu.edu.cn
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Liu
authors.forename: Tianfu
authors.initials: T
authors.lastname: Cai
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhu
authors.forename: Meichun
authors.initials: M
authors.lastname: Deng
authors.forename: Jiayan
authors.initials: J
authors.lastname: Li
authors.forename: Xi
authors.initials: X
authors.lastname: Zhou
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Dan
authors.initials: D
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.forename: Weijun
authors.initials: W
authors.lastname: Hu
authors.forename: Songping
authors.initials: S
authors.lastname: Liang
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000166:cytology; D057809:HEK293 Cells; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D062556:NAV1.7 Voltage-Gated Sodium Channel / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013111:Spider Venoms / Q000737:chemistry / Q000494:pharmacology*; D013112:Spiders / Q000235:genetics / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D061567:Voltage-Gated Sodium Channel Blockers / Q000737:chemistry / Q000494:pharmacology*; D061566:Voltage-Gated Sodium Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D062556:NAV1.7 Voltage-Gated Sodium Channel; D020033:Protein Isoforms; D013111:Spider Venoms; D061567:Voltage-Gated Sodium Channel Blockers; D061566:Voltage-Gated Sodium Channels; C488683:hainantoxin III, Seleconosmia hainana; D013779:Tetrodotoxin
keywords: Inhibitor Cystine Knot Motif; NMR; Nav1.7; Patch Clamp Electrophysiology; Peptides; Sodium Channels; Spider Venom; Toxins