The evolution of voltage-gated sodium channels: were algal toxins involved?

Many algal toxins target voltage-gated sodium (Na+) channels where they act to block or otherwise perturb the function of this critical component of an animal's neuromuscular system. However, many eukaryotes, particularly those that are routinely exposed to algal toxins, have toxin-insensitive or toxin-resistant Na+ channels. Here we provide a brief overview of the structure, function and evolution of voltage-gated Na+ channels, and the structural basis for toxin-insensitivity, as a prelude to a discussion of whether the early evolution of Na+ channels may have been influenced by the presence of algal toxins in the environment.