BcsTx3 is a founder of a novel sea anemone toxin family of potassium channel blocker

Abstract

Sea anemone venoms have become a rich source of peptide toxins which are invaluable tools for studying the structure and functions of ion channels. In this work, BcsTx3, a toxin found in the venom of a Bunodosoma caissarum (population captured at the Saint Peter and Saint Paul Archipelago, Brazil) was purified and biochemically and pharmacologically characterized. The pharmacological effects were studied on 12 different subtypes of voltage-gated potassium channels (K V 1.1-K V 1.6; K V 2.1; K V 3.1; K V 4.2; K V 4.3; hERG and Shaker IR) and three cloned voltagegated sodium channel isoforms (Na V 1.2, Na V 1.4 and BgNa V 1.1) expressed in Xenopus laevis oocytes. BcsTx3 shows a high affinity for Drosophila Shaker IR channels over rKv1.2, hKv1.3 and rKv1.6, and is not active on Na V channels. Biochemical characterization reveals that BcsTx3 is a 50 amino acid peptide crosslinked by four disulfide bridges, and sequence comparison allowed BcsTx3 to be classified as a novel type of sea anemone toxin acting on K V channels. Moreover, putative toxins homologous to BcsTx3 from two additional actiniarian species suggest an ancient origin of this newly discovered toxin family.

Marine Toxins Targeting Kv1 Channels: Pharmacological Tools and Therapeutic Scaffolds

“…Two toxins from the venom of Bunodosoma caissarum were isolated and named, BcsTX1 and BcsTx2 [110]. These peptides contained the classical three disulfide bonding pattern of Kv type 1 toxins and were screened against a panel of Kv channels, displaying no affinity towards channels outside of the Kv1 subfamily.…”

Dynamics of venom composition across a complex life cycle

“…NvePTx1 was originally identified as a homolog of the type 5 potassium channel blocker BCsTx3 from the sea anemone Bunodosoma caissarum (Orts et al, 2013). We also identified bioinformatically several homologous sequences in the sea anemones Anthopleura elegantissima and Metridium senile, and the hydrozoan Hydractinia symbiolongicarpus ( Fig.…”

“…To accurately measure the expression levels of known toxin genes, putative toxins and genes encoding nematocyst structural proteins we used the medium-throughput nCounter platform (see materials and methods), which was previously shown to exhibit high sensitivity and precision similar to that of real-time quantitative PCR (Prokopec et al, 2013). We assayed the RNA expression levels of the genes encoding the sodium channel modulator Nv1 (Moran et al, 2008a), the putative toxins NvePTx1, NEP3, NEP3-like, NEP4, NEP8 and NEP16 Orts et al, 2013), the putative metallopeptidases NEP6 and NEP14 , the poreformer toxin NvLysin1b (Moran et al, 2012a) and the structural components of the nematocyst capsule Ncol1, Ncol3 and Ncol4 (David et al, 2008;Zenkert et al, 2011) as well as the putative nematocyst structural component NR2 (Moran et al, 2014). The RNA measurements were performed on nine developmental stages ( Fig.…”

Structural features of cysteine-rich polypeptides from sea anemone venoms

“…For example, the (π PMTX Pcr1a reversibly inhibits the proton sensi tive channels in the rat spinal ganglion neurons (IC 50 100 nM) as well as reversibly inhibits potassium cur rents in the rat spinal ganglion neurons (IC 50 3.5 μM) [101]. The BCSTx3 toxin inhibits to a varying degree the whole series of potassium channel subtypes expressed in Xenopus (IC 50 , nM, indicated in brack ets): K v 1.2 (172.59), K v 1.6 (2245.93), hK v 1.3/KCNA3 (1006.48), inward rectifier channels Drosophila Shaker IR (94.25), and K v 1.1 (~3000) [102].…”