Mongoose and nAChR



Rikki-Tikki-Tavi and the Nicotinic Acetylcholine Receptor

If you’re a fan of classic children’s stories, you may have heard of Rikki-Tikki-Tavi, the brave mongoose who protected a family from a pair of deadly cobras. But have you ever wondered why mongooses are not afraid of snakes?

Snakes have always been considered one of the most dangerous predators. Black mamba, king cobra, and rattlesnakes are just a few examples that terrify many people. The fear of snakes, known as ophidiophobia, is in fact one of the most common phobias in humans. Why? Because most of the time when we think about snakes, we think about toxic venom and deadly bites.

Most mammals, including humans, are indeed highly sensitive to snake toxins, of which there are about 30 families. One of the families of toxins frequently found in snake venoms is neurotoxins. For example, the venom of black mamba, many-banded krait, or king cobra is primarily composed of so-called alpha-neurotoxins, which bind and inhibit post-synaptic nicotinic acetylcholine receptors (nAChRs) at the neuromuscular junctions and, in this way, block nerve-muscle communication, causing paralysis and respiratory failure in the victim bitten by those snakes.

Intriguingly, mongooses have developed resistance to alpha-neurotoxins via specific mutations in their nAChRs, so that alpha-neurotoxins no longer bind these receptors. This small peculiarity, combined with their lightning-fast reflexes, toxin-neutralizing serum proteins, as well as thick skin and fur, make mongooses fearless snake hunters.

By the way, humans couldn’t ignore the amazing hunting skills of mongooses and decided to use them for pest control for rats and snakes in some areas. So, people introduced mongooses to some islands and… well, it didn’t go well. Mongooses appeared to be much more aggressive predators than expected. At least seven native animal species, including mammals, birds, reptiles, and amphibians, have almost disappeared on Amami-Oshima Island since the introduction of the mongoose in 1979.

So now, the Small Indian Mongoose is considered one of the 100 World’s Worst Invasive Alien Species and is recognized as a threat to global biodiversity. Oops!