Venomous animals such as snakes, scorpions and spiders are typically the stuff of phobias for most people. But the toxins those creatures have developed to immobilize and kill their prey are actually some of nature’s most finely-tuned weapons, sharpened by millions of years of evolution to hit a particular molecular target. For Zoltan Takacs, an Assistant Professor at the University of Chicago Medical Center, it’s those qualities that have made snakes and venom a life-long source of fascination, not fear. From expeditions around the world to catch and collect tissue from venomous animals to laboratory experiments that seek to unlock the potential of those toxins for research and clinical use, Takacs has turned a childhood love of creepy-crawlies into a career.
Acknowledging Takacs’ unique existence as half-scientist/half-adventurer, National Geographic today announced him as one of their 2010 Emerging Explorers. With 13 other award recipients, Takacs earns $10,000 to put toward expeditions that have already taken him to over 130 countries in pursuit of venomous species. Takacs brings tissue from those animals back to Chicago for further study, looking to repurpose the venomous tricks of nature into highly-selective ligands that could have therapeutic value.
“It’s a straight connection between rain forest and lab bench,” Takacs said last week, from a snake-free conference room in Hyde Park. “Nature is not limited to the African savannah with elephants and lions. There is also the underlying molecular biodiversity, and if that’s erased then we lose the potential for new drugs.”
That potential is vast: Takacs estimated that 10 to 20 million different toxins exist in nature. Only 10,000 or so of those toxins have been discovered, and of those only 500 have been thoroughly studied. But from the small supply of well-characterized toxins, at least 12 drugs have already been derived and are currently in use for treating blood pressure, heart failure, heart attacks, and diabetes.
“If you face a heart attack in the United States and go to the emergency room, there are three drugs for emergency treatment and two of them are derived from snake venom,” Takacs said. “These are truly lifesaving drugs.”
Finding more drugs means cataloging more toxins, so Takacs teamed up with biophysicist Steve Goldstein, Professor of Pediatrics and an expert on ion channels, to create libraries of toxins based on templates obtained from nature. A recently published example from Takacs’ research is a vivid demonstration of how those toxins can be reshuffled by scientists to create new compounds even more specific – and potentially useful in the lab and clinic – than their natural counterparts.
The project, published by the Proceedings of the National Academy of Sciences in December 2009, sought to create a specific blocker for a potassium channel expressed on immune system T-cells. In autoimmune disorders such as multiple sclerosis or rheumatoid arthritis, T-cells can be inappropriately activated and will attack a person’s own tissues instead of foreign invaders. Inhibiting a potassium channel, called Kv1.3, can turn down T-cell activity, so a drug that selectively blocks Kv1.3 would likely be a valuable therapeutic tool.
An excellent blocker of Kv1.3 channels comes from an exotic source: scorpion venom. But even scorpion toxins are less than perfect at hitting this target – they cause undesired side effects by simultaneously blocking similar potassium channels in other tissues. So Takacs and his collaborators set about creating a specific Kv1.3 blocker using the scorpion’s venom as a starting point.
“What’s interesting is you still have to go back to nature and pick up the template,” Takacs said. “It doesn’t matter how good we are, the first one still has to be something time-tested by evolution.”
Creating and screening a library of novel toxins took about three years and drew upon expertise from several University of Chicago laboratories. With researchers from the Goldstein’s laboratory, Takacs drew upon the sequences from all known scorpion toxins targeting potassium channels. Shohei Koide helped the group set up a “phage display” assay for testing the potency of a toxin upon an ion channel target provided by Eduardo Perozo, and Thomas Gajewski supplied the immunological expertise for testing the potency.
The toxin sequence dataset allowed the researchers to split each individual toxin into front, middle and back parts, then shuffle all the components like a slot machine with three reels to create hybrid molecules – 11,220 in all, including a handful of native templates.
“That number is likely more than the total number of toxins that have been tested by all researchers from all animal venoms combined,” Takacs said.
The massive library yielded a powerful winner – a novel toxin, dubbed mokatoxin-1 (“moka” means “fun” in Hungarian, Zoltan’s native country), that is highly selective for Kv1.3 without inhibiting other potassium channels. Mokatoxin-1 is a Frankenstein molecule, made up of the front, back and middle segments from three different natural toxins found in different parts of the world. It’s as though evolution ran the first 99 yards of a dash, and Takacs’ team took the baton for the last step in creating a super-specific ligand – “You start with 4 billion years of evolution, then you do the toxin shuffling on top of that to match your particular target,” he said.
Mokatoxin-1 will be a useful tool in the laboratory, where specific blockers are critical tools for experiments, and perhaps also in the clinic as a drug targeting T-cells. But the technology used to create the compound may be even more important. Takacs hopes that their approach can be applied to other toxin families, creating new ligands for favorite venom targets such as the acetylcholine receptor or clotting agents. But the foundation of that research is still old-fashioned fieldwork, and as Takacs told National Geographic, the draw of exploring new lands and wilderness will always remain a major driving force behind his research work.
“Since I need DNA samples from snakes, their prey, and predators, my work requires unconventional travel strategies and ventures into unfamiliar territories – explorations I absolutely love,” Takacs said.