Why don’t poisonous animals poison themselves?
Scientists have wondered how golden poison dart frogs resist succumbing to the high doses of toxin they store in their skin. Certain species of Phyllobates frogs are loaded with enough batrachotoxin—up to 2 mg in adults—to kill more than 20,000 mice, yet their voltage-gated sodium channel membrane protein is immune to its paralytic effects. Sho-Ya Wang and Ging Kuo Wang of the University at Albany now discovered that a single amino acid swap can render sodium channels almost completely resistant to batrachotoxin.
Toxin Resistance in Poison Frogs
The researchers built off a study published in 2016 by another research team that identified five amino acid substitutions differentiating poison dart frog and rat sodium channels. In the new study, scientists tested whether creating the five frog substitutions in the rat sodium channel, individually and in combination, conferred batrachotoxin resistance. Monitoring cells engineered to produce either normal or modified sodium channels revealed that replacing just one amino acid—asparagine with threonine at position 1,584—conferred “exceptional” batrachotoxin resistance (Proc. Natl. Acad. Sci. USA 2017, DOI: 10.1073/pnas.1707873114). Sodium channels with substitutions at the other four locations remained sensitive to the toxin. Sho-Ya Wang says gaining a better understanding of how batrachotoxin interacts with sodium channels may help improve the design of therapeutic drugs that target the same region of the protein. Thousands of animal species use toxic chemicals to defend themselves from predators. Snakes have blood clotting compounds in their fangs, the bombardier beetle has corrosive liquid in its abdomen and jellyfish have venomous, harpoon-like structures in their tentacles. But how do these animals survive their own poisons? Rebecca D. Tarvin details the strategies that protect animals from themselves. bombardier beetle
When attacked, this beetle sets off a rapid chemical reaction inside its body, sending predators scrambling. This amazing chemical defense has some people scratching their heads: How could such a complex system evolve gradually—without killing the beetle too? nematocyst :
Nematocysts are a type of cnidae, and it is the presence of cnidae that separates jellyfish and other cnidarians from other animals. Cnidae are among the most complex intracellular secretion products known.
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