Structural basis for the modulation of voltage-gated sodium channels by animal toxins

Abstract

Animal toxins that modulate the activity of voltage-gated sodium (Na) channels are broadly divided into two categories-pore blockers and gating modifiers. The pore blockers tetrodotoxin (TTX) and saxitoxin (STX) are responsible for puffer fish and shellfish poisoning in humans, respectively. Here, we present structures of the insect Na channel NaPaS bound to a gating modifier toxin Dc1a at 2.8 angstrom-resolution and in the presence of TTX or STX at 2.6-Å and 3.2-Å resolution, respectively. Dc1a inserts into the cleft between VSD and the pore of NaPaS, making key contacts with both domains. The structures with bound TTX or STX reveal the molecular details for the specific blockade of Na access to the selectivity filter from the extracellular side by these guanidinium toxins. The structures shed light on structure-based development of Na channel drugs.

Supramolecular clustering of the cardiac sodium channel Nav1.5 in HEK293F cells, with and without the auxiliary β3‐subunit

“…The epitope recognized by the antibody used in our STORM experiments is located at the cytoplasmic C‐terminus of the Nav1.5 α‐subunit. By comparison with other Nav channels whose near atomic‐resolution structure has been resolved, it is likely that this epitope lie close to or underneath the central pore of the channel, albeit with some flexibility . Observed from above the membrane, a single α‐subunit is an approximate square of length ~8 nm .…”

Tying pest insects in knots: the deployment of spider‐venom‐derived knottins as bioinsecticides

“…Spider‐venom knottins primarily target the DIV VSD (site 3) or the DII VSD (site 4). (b) Top‐down view from the extracellular side of the membrane of the cryo‐EM structure of the voltage‐gated sodium channel Na V PaS from the American cockroach Periplaneta americana (PDB 6A95) . Intracellular regions of the channel have been removed for clarity.…”

“…The TM helices in the DI VSD are labeled. (c) Side‐view of the cryo‐EM structure of spider‐venom peptide Dc1a (cyan ribbon inside grey surface) bound to Na V PaS (PDB 6A95) . Intracellular regions of the channel have been removed for clarity, and domain coloring is the same as in(b).…”

“…Recently, cryo‐electron microscopy (cryoEM) was used to elucidate the first structure of the complex formed between a spider toxin and an insect ion channel . This structure reveals that the knottin peptide Dc1a (grey in Fig.…”

“…(c)); the hairpin makes intimate contact with the S1–S2 extracellular loop of the DII VSD as well as the turret and S5 pore‐domain helix of DIII (pink in Fig. (c)) . Notably, the key Na V PaS contact residues are not conserved in human Na V channels, which explains why Dc1a is insect‐selective .…”