title: Characterization of selectivity and pharmacophores of type 1 sea anemone toxins by screening seven Na(v) sodium channel isoforms.
abstract: During their evolution, animals have developed a set of cysteine-rich peptides capable of binding various extracellular sites of voltage-gated sodium channels (VGSC). Sea anemone toxins that target VGSCs delay their inactivation process, but little is known about their selectivities. Here we report the investigation of three native type 1 toxins (CGTX-II, δ-AITX-Bcg1a and δ-AITX-Bcg1b) purified from the venom of Bunodosoma cangicum. Both δ-AITX-Bcg1a and δ-AITX-Bcg1b toxins were fully sequenced. The three peptides were evaluated by patch-clamp technique among Nav1.1-1.7 isoforms expressed in mammalian cell lines, and their preferential targets are Na(v)1.5>1.6>1.1. We also evaluated the role of some supposedly critical residues in the toxins which would interact with the channels, and observed that some substitutions are not critical as expected. In addition, CGTX-II and δ-AITX-Bcg1a evoke different shifts in activation/inactivation Boltzmann curves in Nav1.1 and 1.6. Moreover, our results suggest that the interaction region between toxins and VGSCs is not restricted to the supposed site 3 (S3-S4 linker of domain IV), and this may be a consequence of distinct surface of contact of each peptide vs. targeted channel. Our data suggest that the contact surfaces of each peptide may be related to their surface charges, as CGTX-II is more positive than δ-AITX-Bcg1a and δ-AITX-Bcg1b.
authors.affiliation: Centro de Biotecnologia, Instituto de Pesquisas Energéticas e Nucleares, São Paulo-SP, Brazil.
authors.forename: André Junqueira
authors.initials: AJ
authors.lastname: Zaharenko
authors.forename: Emanuele
authors.initials: E
authors.lastname: Schiavon
authors.forename: Wilson Alves
authors.initials: WA
authors.lastname: Ferreira
authors.forename: Marzia
authors.initials: M
authors.lastname: Lecchi
authors.forename: José Carlos
authors.initials: JC
authors.lastname: de Freitas
authors.forename: Michael
authors.initials: M
authors.lastname: Richardson
authors.forename: Enzo
authors.initials: E
authors.lastname: Wanke
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004594:Electrophysiology; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology*; D020033:Protein Isoforms / Q000187:drug effects / Q000378:metabolism*; D012615:Sea Anemones / Q000378:metabolism*; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D010455:Peptides; D020033:Protein Isoforms; D015222:Sodium Channels