A poison dart frog is the common name of a group of frogs in the family Dendrobatidae which are native to tropical Central and South America.These species are diurnal and often have brightly colored bodies. This bright coloration is correlated with the toxicity of the species, making them aposematic.
But big question in front of medical science is how these poisonous species are able to survive despite having extreme neurotoxins carried in their body.
poison frog has the most toxic neurotoxin, how it is able to resist the toxin?
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Epipedobatesanthonyi is the earliest source of epibatidine discovered by John Daly in 1974. In fact, Gepirin is named after the genus of this species of frog. Echinopsis has never been seen anywhere in the world and its ultimate source should be an unknown arthropod.
Do not be fooled by their appearance, they are only a thimble size, the whole body is a beautiful color stripes. This is how flat pinch poison frog looks. In fact, it has some of the most potent neurotoxins ever we know. A recent article in Science magazine takes scientists one step closer to solving a daunting issue - why don't these frogs themselves get poisoned? The answer to this question has got great importance in medical fields for issues such as chronic pain and addiction.
The new study, led by scientists from the University of Texas at Austin, nearly solved the issue ,in a small group of poisonous frogs using gemcitabine. In order to prevent them from the predators from attacking them, the toxins are used by these frogs to bind to receptors in the nervous system of the opposing animal, which can induce high blood pressure, epilepsy and even death. The researchers found that the poison toadstools do not get poisoned because of the tiny genetic mutations that occur in them. Only three of the 2500 amino acids that make up the receptor had changed, preventing the toxins from binding to their own receptors. This keeps the safe from effects of neurotoxins. One important thing in the study was observation of the same mutation three times during the evolution of these frogs.
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"Being poisonous is helpful for animals to survive, making them more advantageous over their predators," said Rebecca Tavin, a postdoctoral fellow at the University of Texas at Austin, one of the first authors of the article . "So why are not so many toxic animals? Our work shows that organisms can not evolve without their ability to resist their own toxicity which is a big constraint. We found that three different frogs evolved with the same changes, which It looked beautiful to me. "
There are hundreds of types of poisonous frogs on the planet, each of which uses nearly dozens of different neurotoxins. Thavin is a member of the integrated biology biologist David Kanatra and Harold Zucken's research group, which is devoted to studying how these frogs evolved toxin resistance.
For decades, medical researchers have long known that toxin, a spirobussin, can act as a very effective and non-addictive analgesic. They developed hundreds of compounds based on this toxin, including a new drug that has been in clinical stages but has been ruled out due to some other side effects.
The new study shows how a particular type of poison frog get evolved to retain the brain's ability to bind to toxins - getting scientists to learn more about gemcitabine , which may help to develop better painkillers or drugs for the people that are addicted to nicotine.
"All the information we get about the interaction of these receptors and drugs helps us to design drugs better." Cecilia Burgess, assistant at Wagner Research Center for Alcohol and Addiction, University of Texas at Austin Researcher, another lead author of this article said.
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The unlocking key
Receptors are nothing but proteins that exist in the cell membranes and transmit information both inside and outside the cell. The receptor is like a lock that must be unlocked by a particular key, and when a molecule with the correct shape binds to the receptor, the receptor is activated and sends a message.
The receptors found by Thavin and her colleagues in the study of these poisonous frogs, are involved in learning and memory processes and usually transmit signal when the correct "key" touches them. For unlucky predators, echinacoxin acts like a master key on this receptor, hijacking cells and triggering a phenomenon of crisis.
The researchers found that poisonous frogs using gepirudin, produce a small genetic mutation that prevents toxins from binding to their own receptors. In other words, they find ways to disable the master key. Through evolution, they also found a way to keep real keys working. This means that the lock becomes more selective.
Fighting the disease
The way the poison frog receptors change offers new possibilities for studying new drugs that help fight human diseases.
The researchers found that this mutant, which can produce toxin resistance without affecting normal function, is strangely located in the receptor. It does not come in direct contact with spirobussan, just remains in close proximity.
"The most exciting finding is that these amino acids, even without direct contact with toxins, regulate receptor function in a very precise way," said Burgess. "In the case of a non-toxic substance, the receptors are still working, but once they hit gepirin, they are able to resist in time, which is very appealing to me."
It is important to understand how such small changes affect the receptor function, which allows scientists to exploit this information to develop new drugs. Because the same receptors are involved in pain and addiction in the human body. The study can provide a completely new direction for modern medicine field for a new drug research that helps to stop pain and help stop smoking.
Review evolution
Researchers and Ecuadorian partners collected samples from 28 species of frogs - including those having the neurotoxin spirogin, or other toxins and non-toxic frogs. Thavin and her colleagues, Juan Santos of St. John's University and Lauren O'Connell of Stanford University, sequenced the genes that encode specific receptors in these species. They then compared the slight differences in these sequences and established a phylogenetic tree that represents the evolution of these genes.
This is the second time that a team of Kanatra, Zakun, Tallinn and Sandos participated in the study of the anti-virus mechanism for poisoned frogs. In January 2016, the team identified a series of gene mutations that protect the poison frog of another subspecies from the effects of batrachotoxin. The study, published in September of last year, is also based on their findings. The researchers at SUNY University of Albany have demonstrated that one of the mutation sites proposed by the University of Texas at Austin is indeed able to protect poisonous frogs from toxins.
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