Binding Specificity of Sea Anemone Toxins to Nav 1.1-1.6 Sodium Channels

Abstract

Sea anemones are an important source of various biologically active peptides, and it is known that ATX-II from Anemonia sulcata slows sodium current inactivation. Using six different sodium channel genes (from Na v 1.1 to Na v 1.6), we investigated the differential selectivity of the toxins AFT-II (purified from Anthopleura fuscoviridis) and Bc-III (purified from Bunodosoma caissarum) and compared their effects with those recorded in the presence of ATX-II. Interestingly, ATX-II and AFT-II differ by only one amino acid (L36A) and Bc-III has 70% similarity. The three toxins induced a low voltage-activated persistent component primarily in the Na v 1.3 and Na v 1.6 channels. An analysis showed that the 18 dose-response curves only partially fit the hypothesized binding of Lys-37 (sea anemone toxin Anthopleurin B) to the Asp (or Glu) residue of the extracellular IV/S3-S4 loop in cardiac (or nervous) Na ؉ channels, thus suggesting the substantial contribution of some nearby amino acids that are different in the various channels. As these channels are atypically expressed in mammalian tissues, the data not only suggest that the toxicity is highly dependent on the channel type but also that these toxins and their various physiological effects should be considered prototype models for the design of new and specific pharmacological tools.

Resurgent Current and Voltage Sensor Trapping Enhanced Activation by a β-Scorpion Toxin Solely in Nav1.6 Channel

“…4), we present here data obtained using HEK cells stably expressing the human ␣-subunit of Na v 1.6 channels (20). Previous experiments using Xenopus oocytes transiently expressing Na v 1.6 channels with or without ␤-subunits (28) have shown the presence of small persistent currents.…”

“…25). Molecular biology and tissue expression of Na ϩ ion channels on one hand and purification, sequencing, and structure-function studies of toxin peptides on the other hand, have progressed in such a way that in recent years only comparative studies of the action of very similar and completely characterized peptides on wild type (20) or on mutated isoforms of the same channel provide the means to answer highly specific questions concerning toxin-channel interaction.…”

“…2F, we used ATX-II, a classical toxin that potently slows fast inactivation (3,20). The upper and lower parts of Fig.…”

“…Cell Culture-HEK293 cell lines stably expressing human Na v 1.1, Ϫ1.2, Ϫ1.3, Ϫ1.5, and Ϫ1.6 (generously donated by Dr. J. J. Clare of GlaxoSmithKline, Stevenage, UK) were cultured in modified Dulbecco's medium supplemented with 10% fetal bovine serum as described by Olivera et al (20). Na v 1.4-expressing cells were obtained by stably transfecting a plasmid containing the hNa v 1.4 construct (a kind gift from Prof. Diana Conti-Camerino, University of Bari, Italy).…”

Avaliação da atividade antiinflamatória e analgésica do extrato bruto hidroalcoólico do zoantídeo Palythoa caribaeorum (Duchassaing & Michelotti, 1860)

“…No Brasil existem alguns antecedentes de estudos químicos em cnidários, principalmente anêmonas e octocorais. Freitas e colaboradores trabalham desde a década do 80 com substancias biactivas de anêmonas-do-mar, principalmente com Bunodosoma caissarum e B. cangicum, encontrando atividade antimitótica, hemolítica, neurotóxica e antitumoral em câncer de mama humano Elena, 1991;Lagos et al, 2001;Malpezzi et al, 1995;Oliveira et al, 2004).…”